I tried Stadia last night. Worked really well. I tried The Far Cry 6 demo. Perhaps it's my age but I didn't notice lag. In fact I didn't notice any lag when I played UC1, UC2, UC3 and TLoU on PS Now for PC and FS2020 and FH5 on my OXBO through xCloud.£180 a year to play your Steam/EGS library quality with noticeable lag and reduced image quality.
But some mugs will claim it's a good alternative
It's not as good as native of course but it sure is a good alternative.