Brew for native commandline apps, Distrobox for software that runs on other distros. Boxbuddy (GUI) is an easy tool to create and manage distroboxes, and the default terminal app, ptyxis, allows you to switch distros easily from the top-left dropdown.
And more options in the Bazzite docs https://docs.bazzite.gg/Installing_and_Managing_Software/
some areas have active nextdoor.com marketplaces, but you have to prove your residence by receiving a code in the mail.