ARM is not listed in the “Available Architectures” of Firefox on Flathub: https://flathub.org/apps/org.mozilla.firefox

You can use [librewolf](https://flathub.org/apps/io.gitlab.librewolf-community).

The is some really odd hold up on all official Arm builds https://bugzilla.mozilla.org/show_bug.cgi?id=1677963 despite having it fully working and tested for years.

At least five years ago, it was possible to just apt install firefox on arm. It was a little iffy to get any version other than LTS, though.

I have a cheap Lenovo Chromebook Flex 3 with a MediaTek MT8183 processor that I picked up for under $79 at a BestBuy Black Friday sale. I run Firefox ESR on it with no problems in the Linux container, no flatpak needed. Here's all you need:

sudo add-apt-repository ppa:mozillateam/ppa

sudo apt-update

sudo apt install firefox-esr

Yeah raspbian runs firefox-esr as well.

I have a Lenovo Chromebook Duet (the first gen one) which I think runs the same processor. Though the 4GB RAM is a little bit limiting so I don't use it that often.

There are ARM versions of Firefox available, maybe chromeOS on ARM lacks something else.

Distros ship ARM builds; for some reason Mozilla do not.