confusedreeder

what do you mean you wanted to install applications to an external disk?

if you have a separate OS on the external drive, you could chroot in and install it. If you just want that one application to be on the other disk, you could mount it to wherever on the filesystem the program would be installed. However you probably don't wanna do that on an application by application basis. you could mount /usr/bin/ on the external drive for example. or use LVM to share disk space between the disks

Flatpak, Snap, Appimage and other portable format aren't really preferable. they lead to a software ecosystem that amounts to just downloading and running executable binaries off the internet, each with their own overhead.