@lister-of-smeg thank you very much for your hints, i never thought if trying an optional port, neither i was aware of a version called "Super Big Brother" for the PC-Engine.
Much appriciated!

@libation Thanks for the tip! lr-snes9x2002 is working with the ROMs I tried so far. My ROMs are compressed but their in .sfc format uncompressed, which might make a difference. Although my gamepad is recognized upon load, the controls didn't work on a couple of the games I tried. I guess that'll just require some custom configuring for those ROMs. Cheers

Retroarch 1.8.7 has been released yesterday, hopefully this issue is fixed now.

@mitu Thanks for the addition, I forgot to mention that.

@Addison As mitu said, my tip doesn't apply to HDMI, sorry.

@mikepd213 Re-install all your packages, do an update, then try again. You probably messed up the permissions (executable bit) on your files.

@mitu This worked!

Thanks to both of you for helping me out with this, especially on Christmas day. :)