I'm in the market for an upgrade and will wait until Nov 3 to see what RDNA3 brings to see if it's worth paying for a new card vs last-gen used card pricing.
There is a moonlight host for linux called Sunshine [1]. Works great on Ubuntu and Arch. Just note that it'll use software encoding unless your nvidia driver is patched to enable NvFBC, using nvlax or nvidia-patch [2]. But for non-gaming use, software encoding is more than sufficient with minimal latency compared to vnc.
However, there is an alternative to Nvidia's closed source backend, called Sunshine (argh, the pun): https://github.com/loki-47-6F-64/sunshine
I haven't tried it yet, as I do run Windows /w Nvidia GPU on my desktop, but it apparently uses nvenc correctly (I'm on a Turing, Turing and Ampere have that fancy low latency mode for their encoder; something Steam still doesn't engage for in home streaming, yet uses the nvenc API directly), but also can support multimonitor (has a shortcut key to cycle through monitors).
Moonlight is open-source, you can see in the code yourself as I don't understand most of it. There is also a project that attempt to replace the associated Nvidia Gamestream server but it is quite basic and no longer maintained : https://github.com/loki-47-6F-64/sunshine