These screenshots was taken on Mesa 26.1.6:
Downgrading to mesa 26.0.3 fixes the problem:
System:
Fedora 44 Workstation
Kernel 7.1.8-200.fc44.x86_64
AMD RX 580 4GB
Proton CachyOS 11.0-20260703
Workaround:
sudo dnf downgrade ‘mesa*’ to downgrade mesa from 26.1.6 to 26.0.3 .
Tell me if you need more information about it.
Update:
I’ve been updated to Mesa 26.1.7 and it still same.
I don’t think this is an upstream issue but i’ll keep eyes on that. Need to create an account tho, don’t have a Gitlab account 
I created an issue on upstream:
akamirsky
(Yaroslav Akamirsky)
8
I read in an issue created by the OP that setting this launch variable helps with this issue. If you’d rather not roll back your driver, try this:
radv_disable_trunc_coord=false %command%
P.S. - Created a Fedora account just to write this, btw