[1] https://launchpad.net/~pinta-maintainers/+archive/ubuntu/pin...
Pinta is based on using the engine for one of those with a new Gtk# UI. Though at this stage a lot of that's been rewritten, so it's pretty much just some filters that are used as-is from old Paint.NET.
Even though Paint.NET moves much slower these days, Pinta has moved even slower and the UI rewrite was never as polished as Paint.NET's WPF UI.
Hopefully .net 5 moves us closer to having a Linux version!
Though I do remember accidentally installing it from the default Ubuntu repositories once and it kept crashing really often. Turns out that version is almost 6 years behind the current stable release.