I actually tried this as my second step in trouble shooting, the first being using different ports.
In the non-omada management software, it defaults to 10G, and if the devices is on before the switch it negotiates 10G correctly and works at full speed (tested with iperf3). As soon as any of the 10G connected devices is rebooted, I’m back to 1G. To fix it, I then have to set the port to 1G with flow control on, apply changes, save config, refresh page, change to 10G with flow control off, apply, save config and it goes back to 10G again. Alternatively I can reboot their switch and it’s fine again.
In Omada its the same, fewer steps to get there but I have to sometimes do it 2-3 times before it works.
Same issue with both 10G TP-Link switches, so I’m thinking it might be the SFP. Using Intel SFP+ with FS optical cables. I’m using a DAC for the uplink from the 10G switch to my unmanaged 2.5G switch, and that doesn’t have the problem of dropping, always works max speed.
Have you tried non official jellyfin clients? I had issues with the official app on AppleTV as well, so I switched to Infuse. The free app supports most things and I think the paid gives access to additional codecs if I recall correctly. The pro upgrade isn’t too expensive and the app is sleek across Apple devices. Only issue I’ve really had is sometimes if a video is not played to the end (as in, stopped during credits) it still shows up in the continue watching, but that might be a problem on my end.
I think MXPlayer is similar on Android which might be worth checking out.