Thanks for the report. While i don't have the means to replicate it, i've forwarded the issue to the nesdev discord to see if others have had similar experiences. Maybe they have some suggestions.
EDIT: I got some help from CutterCross. It seems this OS does not support cursors/icons with a colour index representing "inverse from background" - which is why both the precision cursors and the paint spilling out of the bucket aren't showing.
As a first step, i'll add compatibility cursors you can replace with manually. Later, hopefully, i might figure out how to do this smoother for mint users (and potentially others i don't know of).