Forgot to reply to this! With my setup I am using DNSSEC with DNS over TLS to 1.1.1.1. For reference, I have a managed connection, which means I just plug an ethernet connection into a RJ45 connection in the wall and my router picks up a connection as a DHCP client. If I access instagram over a VPN on my router then it works fine over wifi.
When I access instagram the images come through instagram.fdsa1-1.fna.fbcdn.net, rather than
instagram.flhr4-1.fna.fbcdn.net . If I change the image URL to use the domain you specified then the image works straight away over wifi.
If I look up the IP for the URL I have, it gives me 81.23.60.97, which when I reverse gives me a domain owned by my ISP (ip-81-23-60-97.ask4internet.com). I'm guessing that instagram is using some sort of local ISP caching for images and there is an issue somewhere with this?
For your reference, I have given a bunch of MTR results below (from the router, my laptop on ethernet and wifi, along with both the working and not working domains).
From the router:
mtr instagram.flhr4-1.fna.fbcdn.net
OpenWrt (10.93.200.53) 2019-04-17T11:01:56+0100
Keys: Help Display mode Restart statistics Order of fields quit
Packets Pings
Host Loss% Snt Last Avg Best Wrst StDev
1. 10.93.192.1 13.0% 24 0.8 0.8 0.7 1.0 0.1
2. gw-vlan1649.edge2.westone.ask4.net 0.0% 24 1.9 3.6 1.6 27.6 5.5
3. core2-dc1-edge2-westone.ask4.net 0.0% 24 1.8 1.8 1.5 2.4 0.2
4. ip-81-23-51-198.ask4internet.com 0.0% 24 1.1 1.1 0.9 1.4 0.1
5. br2-hex-nh.ask4.net 0.0% 24 4.5 4.4 4.3 4.5 0.1
6. xe-0-0-0-2-9.r04.londen05.uk.bb.gin.ntt.net 0.0% 24 9.7 9.8 9.5 10.0 0.2
7. ae-0.r24.londen12.uk.bb.gin.ntt.net 0.0% 23 9.9 10.1 9.7 13.5 0.8
8. ae-1.r04.londen12.uk.bb.gin.ntt.net 0.0% 23 9.9 9.9 9.6 10.3 0.1
9. 195.66.224.108 0.0% 23 10.0 10.2 9.9 13.3 0.7
10. 213.137.183.101 0.0% 23 10.4 10.5 10.2 10.9 0.2
11. core2-hu0-16-0-4.colindale.ukcore.bt.net 0.0% 23 11.0 11.0 10.6 11.5 0.2
12. ???
13. 109.159.156.65 0.0% 23 11.2 11.4 11.1 14.8 0.8
14. 109.144.0.160 0.0% 23 10.5 10.5 10.3 10.7 0.1
mtr instagram.fdsa1-1.fna.fbcdn.net
OpenWrt (10.93.200.53) 2019-04-17T11:04:21+0100
Keys: Help Display mode Restart statistics Order of fields quit
Packets Pings
Host Loss% Snt Last Avg Best Wrst StDev
1. 10.93.192.1 13.8% 30 0.8 0.9 0.7 1.9 0.2
2. gw-vlan1649.edge2.westone.ask4.net 0.0% 30 1.6 7.5 1.5 89.9 16.6
3. core2-dc1-edge2-westone.ask4.net 0.0% 30 1.8 1.8 1.5 2.5 0.2
4. tor-6-core2-dc1.dc1.ask4.net 0.0% 30 1.8 1.9 1.7 2.9 0.2
5. cache-gw.fna.dc1.ask4.net 0.0% 29 1.5 1.6 1.3 3.4 0.4
6. ip-81-23-60-97.ask4internet.com 0.0% 29 0.9 1.0 0.8 1.5 0.1
The results from the computer (done using WinMTR, I'm on Windows 10)
From the computer when on Ethernet:
instagram.flhr4-1.fna.fbcdn.net
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| OpenWrt.lan - 0 | 30 | 30 | 0 | 0 | 1 | 1 |
| 10.93.192.1 - 31 | 13 | 9 | 0 | 1 | 1 | 1 |
| gw-vlan1649.edge2.westone.ask4.net - 0 | 30 | 30 | 2 | 3 | 12 | 9 |
| core2-dc1-edge2-westone.ask4.net - 0 | 30 | 30 | 2 | 2 | 12 | 2 |
| ip-81-23-51-198.ask4internet.com - 0 | 30 | 30 | 1 | 2 | 11 | 2 |
| br2-hex-nh.ask4.net - 0 | 30 | 30 | 4 | 5 | 12 | 5 |
|xe-0-0-0-2-9.r04.londen05.uk.bb.gin.ntt.net - 0 | 30 | 30 | 10 | 10 | 12 | 10 |
| ae-0.r24.londen12.uk.bb.gin.ntt.net - 0 | 30 | 30 | 10 | 11 | 25 | 10 |
| ae-1.r04.londen12.uk.bb.gin.ntt.net - 0 | 30 | 30 | 10 | 10 | 12 | 10 |
| 195.66.224.108 - 0 | 30 | 30 | 10 | 11 | 37 | 10 |
| 213.137.183.101 - 0 | 30 | 30 | 10 | 10 | 11 | 11 |
|core2-hu0-16-0-4.colindale.ukcore.bt.net - 0 | 30 | 30 | 11 | 11 | 11 | 11 |
| No response from host - 100 | 6 | 0 | 0 | 0 | 0 | 0 |
| 109.159.156.65 - 0 | 30 | 30 | 11 | 11 | 12 | 11 |
| 109.144.0.160 - 0 | 30 | 30 | 10 | 10 | 11 | 11 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
instagram.fdsa1-1.fna.fbcdn.net
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| OpenWrt.lan - 0 | 23 | 23 | 0 | 0 | 1 | 1 |
| 10.93.192.1 - 0 | 23 | 23 | 1 | 1 | 2 | 1 |
| gw-vlan1649.edge2.westone.ask4.net - 0 | 23 | 23 | 2 | 3 | 15 | 2 |
| core2-dc1-edge2-westone.ask4.net - 0 | 23 | 23 | 2 | 2 | 3 | 2 |
| tor-6-core2-dc1.dc1.ask4.net - 0 | 23 | 23 | 2 | 2 | 3 | 2 |
| cache-gw.fna.dc1.ask4.net - 0 | 23 | 23 | 1 | 2 | 7 | 2 |
| ip-81-23-60-97.ask4internet.com - 0 | 23 | 23 | 1 | 1 | 2 | 1 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
Computer on Wifi:
instagram.flhr4-1.fna.fbcdn.net
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| OpenWrt.lan - 0 | 31 | 31 | 1 | 1 | 7 | 1 |
| 10.93.192.1 - 10 | 21 | 19 | 1 | 1 | 5 | 2 |
| gw-vlan1649.edge2.westone.ask4.net - 0 | 31 | 31 | 2 | 6 | 22 | 2 |
| core2-dc1-edge2-westone.ask4.net - 0 | 31 | 31 | 3 | 3 | 11 | 4 |
| ip-81-23-51-198.ask4internet.com - 0 | 31 | 31 | 2 | 2 | 7 | 2 |
| br2-hex-nh.ask4.net - 0 | 31 | 31 | 5 | 6 | 9 | 6 |
|xe-0-0-0-2-9.r04.londen05.uk.bb.gin.ntt.net - 0 | 31 | 31 | 11 | 12 | 19 | 11 |
| ae-0.r24.londen12.uk.bb.gin.ntt.net - 0 | 31 | 31 | 10 | 12 | 19 | 12 |
| ae-1.r04.londen12.uk.bb.gin.ntt.net - 0 | 31 | 31 | 11 | 12 | 19 | 11 |
| 195.66.224.108 - 0 | 31 | 31 | 11 | 12 | 19 | 11 |
| 213.137.183.101 - 0 | 31 | 31 | 11 | 12 | 19 | 12 |
|core2-hu0-16-0-4.colindale.ukcore.bt.net - 0 | 31 | 31 | 11 | 13 | 19 | 13 |
| No response from host - 100 | 6 | 0 | 0 | 0 | 0 | 0 |
| 109.159.156.65 - 0 | 31 | 31 | 12 | 13 | 19 | 13 |
| 109.144.0.160 - 0 | 31 | 31 | 11 | 12 | 19 | 11 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
instagram.fdsa1-1.fna.fbcdn.net
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| OpenWrt.lan - 0 | 32 | 32 | 1 | 1 | 6 | 2 |
| 10.93.192.1 - 8 | 25 | 23 | 1 | 1 | 5 | 1 |
| gw-vlan1649.edge2.westone.ask4.net - 0 | 32 | 32 | 2 | 6 | 24 | 5 |
| core2-dc1-edge2-westone.ask4.net - 0 | 32 | 32 | 2 | 4 | 17 | 3 |
| tor-6-core2-dc1.dc1.ask4.net - 0 | 32 | 32 | 2 | 4 | 17 | 3 |
| cache-gw.fna.dc1.ask4.net - 0 | 32 | 32 | 2 | 3 | 17 | 3 |
| ip-81-23-60-97.ask4internet.com - 0 | 32 | 32 | 2 | 2 | 11 | 2 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider