Thank you!
I'm currently using PikaOS (Linux 7.1.8-pikaos), which is built on Debian Sid I believe, and KDE Plasma 6.5.4 as a DE. Cactus 5.6.1 works without issues. Although on the version before 5.6.1, I had an "Unhandled Exception c0000005" when trying to launch 1.06b with Singling. I know...