You appear to be using Firefox 78 ESR. Any special reason for this version and not the current release as that version might run better on a Mac M1 ?

• https://support.mozilla.org/en-US/kb/update-firefox-latest-release
• Firefox -> About Firefox

About Firefox says I am up-to-date.

You are up to date because you are likely on the ESR update channel for some reason. On Mac this would happen if you were running a no longer supported MacOS 10.9 or 10.10 or 10.11 version, but I don't know why this would happen with an Apple M1 processor unless M1 refers to a specific Mac computer and not to the processor and you updated the OS to 10.15 or newer.

• https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr

The only way to switch the update channel is to drag the 78 ESR version to the trash and download and install the current release.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release