You've been able to enable RT on a SteamDeck with the native (Linux based) OS for about 5+ months now. Performance may vary and it's certainly not going to measure up to a 69xx/79xx series card, but it can do about 30FPS on Doom Eternal, at the native 800P screen which is pretty neat for a portable running an APU :-)

6xxx does support it, it's just slower than 7xxx. I don't bother because I don't want the perf hit (even with these improvements) as I care more about high refresh rate/resolution support but good to see nevertheless, particularly for future cards where performance will improve further.

You might want to upgrade Mesa too as I believe at least some of the RT options should now be enabled by default, but I haven't tested myself. And you can force it with env variables, as the other commenter suggested.

I case you want to try it out, the setting I've used in Steam was:

RADV_PERFTEST=rt VKD3D_CONFIG=dxr11 %command%