As Chimera is a Musl-based distribution with a small repository, you may want to use Flatpak to supplement the existing software sources, e.g. when using proprietary software.
Full GNOME setups have it installed by default. Smaller setups may need to install it manually:
# apk add flatpak
For proper functionality, you may need to install an appropriate XDG desktop portal implementation.
For GTK there is xdg-desktop-portal-gtk, with xdg-desktop-portal-gnome
for additional GNOME infrastructure integration. For Wlroots-based Wayland
compositors, xdg-desktop-portal-wlr should be used.
Repositories
By default out of the box, Flatpak is not very useful. You may want to add the Flathub repository at very least. You can do so like this:
$ flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
Afterwards, you can use the flatpak command to install, remove and upgrade
software. For instance, to list available stuff:
$ flatpak remote-ls
At this point you may also use frontends such as GNOME Software to manage it (do note that it may require a restart and may take a while to come up as it needs to refresh its metadata).