Get off systemd, and enter the world of chroot.

I run a fairly ancient RedHat Enterprise 6 on my 32-bit test machine and if I need something requiring Gtk3 (such as a latest Firefox or Chrome), I just make a chroot and use debootstrap (from EPEL) to get me a Debian 9 userland for that program. Easy. No bizarre "app stores", no conflicting packages. Do people use Snap app-stores because they don't know how to use the chroot command? Or are they just lazy? If it is because they want the added security of a container, substitute chroot with lxc... Shouldn't be necessary though; if you avoid non-ethical software (i.e App-stores), you are very unlikely to need the added security.

Reinstalling a kernel from a chroot