Hello! I've tried to run Krita 4.1.7 as Appimage on Ubuntu 18.10 and Elementary OS Juno. Something strange with the theme. It seems to be broken.
I feel that I need to additionally install something but I just don't know what Here is a screenshot https://drive.google.com/open?id=1sSLCzLbVAB7sjJOtcRgdR-9CAIcpdTPY

Settings->configure Krita->general and there toggle the 'high dpi' button. No idea why it is so strange looking on your system in the first place though.

Thank you very much! It solved the problem indeed.