TBH it sounds like you're doing this on hard mode. I use and recommend a Roku streaming stick (which does support netflix 4k) and jellyfin. You're using proxmox so you've already accepted a proprietary component to your stack. Unless you are using the PC in your tv cabinet as a PC, it will be sub-optimal as a client device for streaming services via TV compared to a Roku or equivalent.
Since I'm sharing the Netflix account with my siblings, I can't use a smart TV, a Roku or another player but just a browser, because the hardware players should all be using the same Internet connection.