Comment 1 for bug 1890916

Many users reporting crashes and disappearing of Pinta. In most cases the problem is because Ubuntu 18.04 has by default installed old version of Mono, that Pinta depends on.

Please check mono version of you computer: mono --version
If it is older then 6.10 then please upgrade Mono by following instructions:
https://www.mono-project.com/download/stable/#download-lin

Please report back if new Mono version fixes a problem in your case.