@Axel-Spoerl Thank you for your answer

@Yash001 this is just general advice. on linux, to run commands as part of the installation is usually handled by postinst.src if deb based, or under %dir section (.spec file) if centos based distro, which are part of respective .rpm or .deb files.

If you only have one controller, a more flexible approach would be to take the first value returned by the QGamepadManager rather than hard coding it like that. It's not guaranteed that you will have the same value each time.

One possible alternative could be to use a Docker container to build your application with a suitably old Ubuntu or maybe a VM which would be even simpler,

The online installer provides 5.15.2.

It also provides a more recent version of Qt Creator which might work better than the one you are currently using.

@gandsnut
Ok. so it looks like whatever MS app is is pulling in its own versions of system libraries instead of using the default ones. Maybe its time to go to the application support channel for that tool. It's not a Qt specific question at this point.

I haven't solved the problem yet, but I know what caused it.

QtCreator is doing what it's supposed to, that is, finding the 5.15.1 libraries correctly.

My problem is that my Cutelyst version was built with Qt 5.12.8. CMake automatically found and used the Qt 5.12.8 libraries I have installed, which allowed the version built with only CMake to run correctly.

So, I built a Cutelyst version manually using the 5.15.1 libraries instead. I'm having trouble getting CMake to detect that version, but that's a separate issue, so I'll close this one.

I suspect that a combination of CAP_IPC_LOCK and/or CAP_IPC_OWNER capabilities applied to the executable will probably help.
See setcap man page.

Found out that this error only occurres in Qt Creator version installed with online installer. The one installed with apt-get works just fine, so I will stick to it.
Sorry for wasting your time

Thank you!
No, partly because the QtSettings are a bit scattered and I wasn't shure which ones would be correct.

Removing and reinstalling QtCreator from Ubuntu repos didn't work, but removing and installing it via the QtUnified online installer did. Was hoping to avoid that because I didn't want to log in with an account but gave up eventually. I may try to switch back with cleaned settings at one point, but for now I'm just glad it works again.