Cannot create steam game folder "new steam folder must be mounted on a file system with execute permission"
The order of options in /etc/fstab is important and user sets noexec. Since I had exec before user, the noexec from user took precedence over explicit exec. /etc/fstab should be changed to:
UUID=8c6ead8f-bf5f-41b9-864e-d743ad374636 /run/media/marcel/games ext4 defaults,user,nofail,exec 0 0