I did run our unit tests on HEAD of master (6fc658dd54f139b20f858e5089d0baa860bb8300) on - Manjaro KDE Plasma - Arch KDE Plasma - Arch console-only with success (all unit test succeed). I am in contact with the Arch AUR pkg maintainer "graysky" to retest it (internally only - not as release candidate): https://aur.archlinux.org/pkgbase/backintime#comment-888281 @buhtz

QPainter::begin: Paint device returned engine == 0, type: 2\nQWidget::render: Cannot render with an inactive painter

I could NOT reproduce the QPainter output you have mentioned in a comment of #1353 (neither in Arch console-only nor via SSH on Arch console-only - Arch was a fresh VM installation!) so I would ignore this problem until it pops up again or you can hunt it down on your machine.