TL;DR

rpm-ostree override reset firefox
(reboot)
rpm-ostree rebase fedora:fedora/37/x86_64/silverblue
(reboot)
rpm-ostree override remove firefox firefox-langpacks

Explanation

With Fedora 37, the Firefox package has been split into two, firefox and firefox-langpacks.

Some people choose to remove the base Firefox in favour of the Flatpak, but this will cause an error like the following when trying to rebase:

error: Could not depsolve transaction; 1 problem detected:
 Problem: package firefox-langpacks-106.0.4-1.fc37.x86_64 requires firefox = 106.0.4-1.fc37, but none of the providers can be installed
  - conflicting requests

The easiest solution to this is to re-add the base Firefox, then rebase, then remove it (along with the langpacks) afterwards.