I understand you're not support for Krita but I'll ask
Are you using wayland with krita? Tablet seems fine with x.org but when running Krita under wayland it exhibits odd issues (not resetting cursor when pen is no longer tablet but is within range for tracking).
Also, sick sketches :D
Of course I'm not using Wayland. This thing is not appropriate for painting (no advanced configuration for tablet like xsetwacom, latency and lag issue, lower performances, double cursor issues, and focus issue as you describe, etc... ). This technology is far to be mature, it might work for people living in a world made of a terminal and a web-browser only 😆