I'm using media-gfx/flameshot on my arm64 machine, it work well, please keyword arm64.
tatt reports also looks good: USE tests started on Wed Mar 1 02:14:50 AM CST 2023 FEATURES=' test' USE='' succeeded for =media-gfx/flameshot-12.1.0 USE='' succeeded for =media-gfx/flameshot-12.1.0
arm64 done all arches done