Comment # 80 on bug 110659 from tempel.julian@gmail.com

Oh my. I've tried the oldest Proton build offered by Steam, which is based on
Wine 3.7, and indeed it doesn't show the issue (neither in Oblivion with
wined3d OGL nor Hitman 2 DXVK Vulkan). I tried with the older Proton 3.16
version before, which unfortunately is the one that started showing the issue.
I don't know why I didn't try 3.7 in the first place. I'm sorry for the time
you have invested into this issue. :(
Though it would appear to me that the old non-atomic DC is very resilient
toward such issues.
To be sure, I also tested with untouched Arch 5.2.13 kernel: Without that Wine
commit, it is totally free of that stutter issue as well.

Pierre-Eric, I reverted that commit c6b6935bb433dbbd30f5ba122a7c45ad3a2d6eed,
and indeed, it introduced this issue. Should I create a Wine bug ticket for
this?

Closing now. Big thanks @ Michel and Nicholas for their great support. AMD's
kernel and Linux windowing support is simply outstanding, a dam good reason to
stay with team (former) red. :)