Thanks for the info.
Probably it's time to swith on the mesa 22.3.7 for Slackware 15.0?

Although RX 6000 series CPUs have been out for awhile, we all know that it does take awhile for updates in mesa and kernel to trickle into Slackware, specifically into 15.x or 16.0. As I mentioned somewhere on LQ earlier, for Slackware-15.0 Stable I've upgraded to mesa-22.2.5 and libdrm-2.4.115 (required for mesa) for the RX 5700 XT box running Steam/proton/Wine. This is about as new as you can go without needing to upgrade a whole bunch of other core packages to get what will essentially be the next release. The miniITX with the RX 6650 XT runs fairly well on stock 15.0, and I'll wait for the next release (when I build a new gopher and game server) to update and move it to the living room 4K TV as my casual Steam console. The only weird regression that popped up for the RX 6650 XT were random lockups on kernel-5.15.94. Previous 5.15.80 worked fine. Known issue for various kernels. The workaround for me was to swap from display port to HDMI.