Originally posted https://steamhost.cn/steamcommunity_com/groups/homestream/discussions/1/595144081821151445/ but it turns out this is also happening to Game Recording.

Recording from a Dell Inspiron 14 5430 running Debian Testing
CPU: 13th Gen Intel(R) Core(TM) i7-1360P (16 cores)
GPU: Intel(R) Iris(R) Xe Graphics (RPL-P) (driver 1.4.305)

Example with a fairly complex image just in case the pattern of where the pixels are ending up is relevant:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3448744839
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3448745968

Changing the hardware encoding setting does nothing, likely because it's an integrated GPU. Setting it to use HEVC crashes Steam on game startup.