Here are the results I got:
this is from my Debian server (which is another 5+ year old laptop) with a TP-LINK UE300 USB3 adapter: (this did hit 900+ a few times)
this is from my Rpi4b:
and this is from my Windows 10 desktop using CMD/curl:
edit: I'll have to try the Windows 10 test with my laptop connected directly to the LAN switch. It's a newer device than my desktop.
I think the fact that your Debian Laptop with UE300 can hit 824 Mbps average and into the 900's instantaneously, suggests that the bottleneck is actually the CPU on your old machines not the Bell device or router or smart switch etc.
The reason for download direction being slow is probably that the process of receiving packets is generating a lot more interrupts than sending.
I think youāre %100 right.. 
I was convinced it was something else since I was able to get great transfer rates using iperf3 between my Debian server, Windows desktop and my Rpi4 router. (900+ Mbps)
I guess Iāll get my best test results with my daughterās newer gaming laptop tomorrow.
These tests also confirm how unreliable and inconsistent Speedtest.net results can be as I ran several tests directly from my Debian server and always got results between 400 and 500āish.
I know the web version does āmultiā server tests. The shell version only does single server tests if Iām not mistaken.
Another test from my Debian server:
You should try Cloudflare's speedtest:
Cloudflare has always been able to saturate my connection and I love the way they present the data, you can tell it was built by engineers.
I tried this, and the speeds aren't that great for my area. Even though I'm closer to Toronto, it's automatically choosing a server in Chicago 
Even though my devices seem to be the reason for my low downloads and high upload speeds, I'm still not convinced it's the same issue all my other devices are experiencing.
I have an iPhone 11, which I used to get roughly 400Mbps+ when my service was Fibe 500 (the cap was 500Mbps). Now I only get 100'sum Mbps with double upload speeds (200'sum). Even my desktop and laptop used to get nearly 500 speeds. Now I get 1/2 of that..
I really don't understand fully what's going on.. I even researched my MTU for my connection type.. and it's set to 1492 on the WAN interface.
There's "something" I must be missing in my configs.. even if I try plugging in directly to media converter. I may just revert back my internet package back to 500.. since I really don't see any benefits right now.
Another example is my wife's MacBook Air on our wifi:
Speedtest by Ookla - The Global Broadband Speed Test
well I guess my wifi is crap too lol
this is a test between a macbook air and my debian server.. I'm like 8 feet from my DECO M4 which is connected via ethernet to my switch.
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-60.00 sec 407 MBytes 56.9 Mbits/sec sender
[ 4] 0.00-60.00 sec 406 MBytes 56.8 Mbits/sec receiver
[ 6] 0.00-60.00 sec 333 MBytes 46.5 Mbits/sec sender
[ 6] 0.00-60.00 sec 332 MBytes 46.5 Mbits/sec receiver
[ 8] 0.00-60.00 sec 685 MBytes 95.8 Mbits/sec sender
[ 8] 0.00-60.00 sec 685 MBytes 95.7 Mbits/sec receiver
[ 10] 0.00-60.00 sec 352 MBytes 49.3 Mbits/sec sender
[ 10] 0.00-60.00 sec 352 MBytes 49.2 Mbits/sec receiver
[SUM] 0.00-60.00 sec 1.74 GBytes 248 Mbits/sec sender
[SUM] 0.00-60.00 sec 1.73 GBytes 248 Mbits/sec receiver
I'm not the only one who's reports this.. slower download speeds withe Bell's 1gig+ service..
Hmmm. Maybe try turning wifi off and on again so that the macbook is actually connecting to the closest M4 unit. WiFi of course depends on a bunch of stuff, how wide are the channels you're using, which interfering signals are there, 5GHz vs 2.4GHz and etc etc.
That's a generally acceptable wifi speed though. I mean, more than that probably requires 80 or 160 MHz channels or whatever. You're generally better off with more wifi access points on more narrow channels if you have multiple devices in your LAN. I don't tend to worry about max throughput on wifi. If I need throughput I plug in.
could a defective SFP module cause download/upload issues? I currently have a Nokia G-010S-A.
I tried to see if I could find an alternative on Amazon (to test) and only found this one:
Generic Module GPON-ONU-Class B+1 RTXM167-431 SFP: Amazon.ca: Electronics
I've read on some sites that some people have experienced performance issues with a wonky SFP module. Maybe I could even ask Bell to switch my Nokia SFP for a Huawei or Alcatel-Lucent.
It's the only component I haven't switched yet.
It could be, but ... Eh, not likely. I mean it seems more likely it's a systemic issue like oversubscribing your local loop or something.
I'd suggest just dropping back to the 500/500 symmetric and be content w that, as long as it remains low latency
You might also try hitting a public iperf3 server with a UDP burst and see how much packet loss and delay you experience each way
I may end up doing that. It was only $10 to go from 500 to 1000. I figured it was worth it.
Now uploading speeds are amazing.. itās just my download speeds that tanked.. I was getting 500+ Speed tests from almost every wired device I had on the 500 plan 
Still baffles me
I tried to find nearby servers and thereās only 2 I could find in the US and the speeds arenāt the greatest. Iād have to setup my own test with someone else on Bell nearby.
This is interesting. I agree it's baffling, but see what happens with the higher end laptop your daughter has... If it's able to saturate the connection it'll be interesting.
Also are you running SQM? Also did you follow the advice about RPi enabling RPS from the thread @moeller0 mentioned at the very beginning of this thread?
Yeah sheāll be home tomorrow so Iāll give that a try for sure!
No I donāt have SQM enabled. I also verified on the managed switch thatās itās not enabled.
What thread are you referring to? I donāt see any mention of RPS in the one link I found. Unless Iām missing the reference.
See image where you can check the box for packet steering (RPS is receive packet steering)
Can you ask them to switch you back to 500 temporarily?
I suspect that 1Gig plan would require your SFP transceiver to operate in 2.5G mode, while the 500M plan just sets the transceiver to 1G mode 
Who knows, maybe 1G plan under 1G transceiver mode doesn't work well with the MC220L? I didn't read your updates recently but maybe also try the 10Gtek one
Tried this (and rebooted) and I'm getting similar results unfortunately 
I got them to do that last time I spoke to their Support and my download speeds were still around the 500 mark. So it's hard to know if it made a difference or not.
I was going to try and test using another SFP, however I need a single port one. Amazon doesn't seem to carry too many of those. The only one I found was this one: Generic Module GPON-ONU-Class B+1 RTXM167-431 SFP: Amazon.ca: Electronics
I did try these tests with my SFP connected directly to the Bell router/modem and I'm still get similar results as when I'm using the MC220L.
Do providers have the ability to switch the mode the SFP operates in? That would explain a lot.
This thread seems to support this theory:
https://www.reddit.com/r/Ubiquiti/comments/gftj52/dream_machine_pro_canada_bell_aliant_15gbps/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
Bell doesnāt support 2.5G mode syncing unless youāre using their devices directly. This is why I lose 500Mbps on downloads 
ā You will only get around 800 down and 920 up, the UDMP will not sync to 2.5G that the bell SFP uses, and something to do with buffering slows it down more when synced at 1G.
there is some light though, UI-Glenn has stated that 2.5G sync on the UDMP is on the road map, so it sounds like its a software thing and not hardware.ā
More discussions about this here too:
https://www.reddit.com/r/Ubiquiti/comments/gh338z/dream_machine_pro_slow_wan_sfp_speeds/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
Is there a media converter thatās reasonably priced that supports 2.5G? That Edge router is kinda out of my (wife-approved) price range 
Iām going to try plugging in my Rpi4 directly to one of the LAN ports of the Bell router/modem again and see what I get. Iād have to plug the SFP directly to it again since itās apparently able to handle 2.5G. Itās too bad the HH3000 doesnāt support bridge mode.
Hopefully Iāll also have my daughterās new gaming laptop with me to test that throughput too. 
My personal preference is for low-latency with good bandwidth over high bandwidth with high latency. If you have 1.25 or 1.5Gbps fiber connecting to 1Gbps ethernet, there will be a buffering issue at the transition between 1.25/1.5 and the 1Gbps ethernet. To accomodate that you'll wind up wanting to run SQM and you'll have to set your speeds to something somewhat less than 900Mbps most likely.
You may well get better quality of connection at 500Mbps measured in terms of your satisfaction with the service, particularly if you have any gamers or video conferences or other interactive media.
Rather than spending money on trying to get the fastest thing you can, I honestly suggest considering upgrading to a TP-link T1600G-28TS as your core switch, which will give you an SFP slot you can connect to your fiber, and nice QoS settings, IGMP/MLD snooping, and such settings. Save $10/mo by running 500Mbps and in a year you'll have paid for the switch. The RPi will handle SQM at 500Mbps without any problem at all, and you'll have reliable low latency and relatively high bandwidth.