I have been using Krita with a Wacom One 12 on Ubuntu for about a year. During that time the versions of both Ubuntu and Krita have advanced. (I usually upgrade Ubuntu and other apps every time I know of new versions.) Yet, since I installed 26.04, the Wacom stylus has totally refused to function while using Krita. I was using 5.3.1 in a flatpack when this happened. The stylus works in other apps including Chromium, Firefox, Gimp, LibreOffice, Nautilus, Okular, and ptyxis. (It doesn't work in Emacs, but that's neither necessary nor surprising.) While keeping the latest release of Ubuntu, I have tried Krita in an older flatpack version, a Snap version, and both 5.3.1 and 6.0 AppImage versions. The stylus is completely unresponsive when operating in any of these versions of Krita. My computer is a System76 Gazelle 17 (4 years old).
It's likely that this is an xwayland issue, see: https://krita-artists.org/t/krita-5-3-on-ubuntu-26-04-wacom-not-working/183761