Remove Flathub apps on Chromebook

I have downloaded two copies, different versions, using Flathub. They both show up in my Linux apps on the Chromebook. How do I delete the older version? Obviously, I know very little about Linux.

An example would help, e.g. flatpak list | grep APP-ID.

Anyway, if you have two copies of the same APP-ID and you run flatpak uninstall APP-ID you’ll be asked which one you want to remove.

If the installed apps have different branches, you can specify which branch you want to remove, e.g. flatpak uninstall APP-ID//BRANCH.

There’s no such an example where a first user might expect it:
https://docs.flatpak.org/en/latest/using-flatpak.html#remove-an-application

but it’s explained before in the docs:
https://docs.flatpak.org/en/latest/using-flatpak.html#identifier-triples