fwiw, newer firmware dated May 2022 is available from TPLink's US website.
https://www.tp-link.com/us/support/download/archer-ax50/#Firmware
Archer AX50(US)_V1_220526
If you compare the previous releases for US and EU, the actual firmware .bin image for AX50 has the same filename and are identical when binary compared.
It may contain a fix for the Homeshield bug?
Would installing a separate DHCP server on the LAN solve the DNS issue?
ie. don't use DHCP and DNS servers on the stock AX50.
Oh, I mean, I don't need those speeds for the VPN-connected devices if that's what you mean, just any remote acces to my NAS at all is fine haha
I'm sorry if this is a dumb question, but does that mean, for my lack of a better description, "any Windows-compatible PC?" I'm a little worried about intercompatibility with the various network cards, as there's so many I wouldn't even know where to troubleshoot if something went wrong haha.
networking specific mini-PCs
Is there a whole market for those devices? You're blowing my mind a little right now.
Shouldn't I be fine if I connect the built-in port to a (managed) switch and route everything thorough it including the modem? Or is the built-in port not Gbit capable, or is there another issue I'm not seeing?
Nano R4S has two ports and is a decent option
You're not the firs to suggest that board, but I would rule out all of these because there's no way I'm getting my hands on one in a reasonable timeframe or for a reasonable price. I wouldn't be bringing the RPi 4B 8GB specifically into the conversation if I hadn't been in a waiting list for one for half a year now.
wrt3200acm or wrt32x
I have seen many recommendations for these and would go for one if I could. Unfortunately none are available that wouldn't require overseas shipping to where I am.
Interesting, I only check for online updates in the web UI and the last one I got was 30/07/2021.
It may contain a fix for the Homeshield bug?
If you read through the articles, they only admit that the bug was that there were too many DNS requests, not that they were sending all data to Homeshield regardless of whether you enabled it or subscribed to it at all. Still not a very good situation.
Would installing a separate DHCP server on the LAN solve the DNS issue?
I actually do have Pi-hole with DHCP enabled on the LAN and all my devices query DNS to it fine. The router even lets you change the DNS server broadcasted by the DHCP server to one on the same LAN. What it doesn't let you do is change its own uplink DNS server to one on the same LAN, which it uses for the DNS requests generated by itself / queried to it directly.
Like the one in Need a reliable OpenWrt router/wifi box - #40 by phinn
and Advice on N5105 mini-PC's - #2 by shdf
While you can get ARM64/aarch64 platforms that does several Gbit/s they're still "niche" meaning that they're rather expensive and/or only partially supported as most rely on hardware processing which usually isn't supported in OpenWrt (and may also apply to mainline Linux).
You should also be aware that OpenWrt mainly targets low power/performance so you're going to miss out on newer hardware features unless you patch and compile your own firmware. If that doesn't sound appealing just look at another distro such as opnsense and/or pfsense for instance (x86 only) or at running a full blown OS.
As it is right now I wouldn't recommend you to spend a lot to get "multi" Gbit capable hardware, just get something that does Gbit speeds and upgrade further down the road once it's actually needed. I would also like to stress that SQM is not by any means some kind of requirement especially on high speed connections (it does indeed serve a purpose however) as it will kill performance on Gbit connections due to its single threaded processing.
Just go with something like this and some kind of of AP/Mesh system (these are easily found on eBay from Germany)
I personally run several RockPro64's (https://www.pine64.org/rockpro64/) with an additional PCIe NIC that runs rock solid but there's a bit more thinkering involved however I'm very happy with the result. Unfortunately these boards aren't very common in the EU yet. You can also replace pi-hole with something like https://github.com/0xERR0R/blocky or some solution using Unbound to avoid having to run a separate device and/or a VM.
Edit: Don't type replies in a hurry 
if you live in england you have a belkin rt3200 good routeur for cheap price
Oh. I wonder why I never learned that when I was researching open-source FW, OpenWRT always came out on top for pretty much everything. Is the same true for DD-WRT?
Looking a bit deeper into it now, I see quotes such as
I want to have wireless in my router. That's easy! You should use OpenWRT. [...] You should NOT use pfSense or OPNSense - they don't support 802.11ac and have sub-optimal 802.11n support.
from here (teklager.se), but also
what ended up switching me over [to OPNSense] was the multi-wan support. It just isn't very good in OpenWRT.
from here (OPNSense subreddit).
I'm also a little skeptical about the fact that OPNSense/PFSense seem to market themselves as firewall FW, not router FW. I'd love to read more if you happened to have some good resources, so much of the internet is filled up with wirte-fast-say-nothing articles that I don't know where to look. It seems that an OPNSense router-only box + separate APs w/ OpenWRT would be an ideal setup, like the one you linked?
I also can't find a list of supported devices for OPNSense (apart from this HW requirements support page), is it just any x86-64 machine? Does OPNSense actually run as a program on a standalone OS?
I'm sorry for so many questions, I am learning a lot right now.
Unfortunately, not from England and the RT3200 isn't available here either. I'm starting to think there's a mob controlling what can be sold here haha
I think so, the missing point in that list is IMHO is "low cost"... or put differently OpenWrt IMHO aims at making the traditionally cheapish cost-optimized "home-routers" more usable by allowing users to escape the traditionally tight constraints of the original firmware and extend the lifetime by (often not always) offering much longer software updates and even new features. Such devices are still often severely limited in storage size so OpenWrt put a lot of emphasis on keeping things small (constraints that do not really exist in middle to upper-end x85/ARM computers).
So both OpenWrt and I guess DD-WRT (never used it myself so no first hand experience) have a decent reason for existence, but driving state of the art hardware capable of doing interesting (CPU-intensive) things at the top end of consumer internet access link speed is not really one of these reasons.
Check the feature set of OPNSense/PFsense before you go that route; very likely that this is a decent match for your requirements, just not guaranteed. Firewalling is traditionally somewhat harder than pure routing (which after all with a few settings any linux or freebsd box will do for you) so I guess this is where the "senses" pitch their capable firewall (and firewall control GUI) hard, as these add the value.
For a All in One with full OpenWRT support that does multi gig I'm only aware of the Turris Omnia 2022.
I thought current omnias can operate their SFP cage at 2.5 Gbps (with the right sfp module), but they have neither a 2.5 Gbps switch nor a second 2.5 Gbps ethernet port.
Measurements taken a few years ago showed that sqm works on an omnia up to 500/500 Mbps for bidirectionally saturating loads (with sch_cake). Others reported up to around 1000 for unidirectional loads....
I'm talking of the 2022 model (or maybe it will be called Turris Omnia 2?) which will have a quad-core 64-bit processor, at least 4 GB of RAM, Wi-Fi 6 support, two 10GE interfaces and m.2 slots
Both OPNSense and pfSense are based on FreeBSD so in general the same hardware support applies which is more or less "any" x86 box although I would highly recommend you to stay away from Realtek NICs.
That is more confusing than helpfull to link the specification of the old model.
As you can see here https://forum.turris.cz/t/turris-omnia-2022/15995/124 there is quite a difference between the old and the new model
it was the only specs available on turris's website.
Well, currently to the best of my knowledge there only exist prototypes of a next generation omnia, so I would take any feature desriptions more as a statement of intent than of fact, with the current supply chain issues the question might boil down to which parts are actually attainable in the desired quantities versus which parts would be nicest to have.
ATM the published specs @KOA posted describe those omnias well you can actually buy... I would respectfully say, the coming omnia is a bit off-topic for this thread as it not currently available (in the EU or any other place). From the announcement which posted the tentative specs:
"Unfortunately, no ETA yet. But we aim for 2022."
There is nothing else announced that would match
so off course I drop the new omnia here since it is the perfect fit and even if you wait a few months more there will be nothing comparable.