Flatpak Firefox 112 not showing (some? bitmap?) fonts in Debian

I don’t know why I’m struggling with flatpak’d software so much.

The problem

Today, it’s flatpak-installed Firefox 112, not loading some (bitmap?) fonts, meaning I get a text-free page:

Page of website not showing some fonts, so just big whitespace

Yes, I can make it work but this bug has seemingly been around for 3 years, and it is a pain to remedy if your browser is not displaying text…

The workaround

Create the necessary directory: mkdir -p ~/.var/app/org.mozilla.firefox/config/fontconfig

Create a file for editing: vim ~/.var/app/org.mozilla.firefox/config/fontconfig/fonts.conf

Paste this:

<?xml version='1.0'?>
    <!-- Disable bitmap fonts. -->
        <patelt name="scalable"><bool>false</bool></patelt>

You may need to restart Firefox to make it work; I don’t think I did, but I wasn’t paying enough attention.

The outcome

Webpage, now showing text

Why am I here?

The version of Firefox in the Debian apt repo is rather old (not a surprise).

I don’t want a standalone .deb, as I like easy/automatic updates. (See below)

So I have options of either snap or flatpak.

I can’t remember why I picked flatpak over snap.

Neither is perfect, and I’ve had fun with both to fix:

Update 2023-04-17

Apparently - according to people in the fediverse, anyway - the Mozilla-supplied .deb file does auto-update.

So I am going to try that for a while.

I followed this guide, but I ‘chown’d the directory /opt/firefox to my user, rather than root, so that I could run it from there, as me.