Recently (3rd April) after updating Mesa to 21, not all but many application was unable to render properly, including
konsole (last two used transparency) were unaffected. Starting
plasmashell from terminal didn’t produced any informative debug statement. I pulled
vulkan-intel 20 from stable and problem was resolved.
I again tried to update today, along with newer update of
mesa-vdpau, but problem persisted.
GPU: Intel HD Graphics 4400 Compositor: xrender GPU driver: i915
I just notice (while writing this, to find GPU model) the GPU is reported to be
llvmpipe (LLVM 11.1.0, 256 bits) in
OpenGL renderer string of
glxinfo which used to be (last seen months ago),
Mesa DRI Intel HD Graphics 4400 (HSW GT2) (Collected from inxi output on 10 June 2020)
I recently tried some VNC and also using Weylus.