Chromium not starting on Ubuntu 20.04

I just got this problem, seemingly out of the blue. Turns out I may be related to a problem I already reported about fonts not loading in the Chromium Snap.

I found the following workaround :

# first close all instances of chromium
sudo rm /var/cache/fontconfig/*
rm ~/.cache/fontconfig/*
sudo fc-cache -r -v
rm -rf ~/snap/chromium/common/.cache/fontconfig/
chromium-browser

This set of commands is a workaround for a problem I already reported here : [chromium] File chooser is not displaying font

Thanks to the fundamental observations from the Antoine Pintout answer, I recalled that I had installed several new fonts, not included in the Ubuntu base system.

A first effect was that the "Save page" window in Chromium was no more able to use any font, displaying instead a vertical empty rectangle ▯ for each letter. It is exactly the same issue as in the Antoine Pintout linked report.

However, Chromium was still working. Then, after some days, it presented the issue of my question.

Yesterday and today, Ubuntu deployed several updates that I applied: between them, snapd and xorg-* (but not xserver-xorg-video-intel). After the updates, Chromium still didn't start.

Instead of using the workaround suggested by Antoine Pintout, I simply removed the fonts I had installed, and the issue disappeared: Chromium was able again to start. I don't know if the recent updates contributed to this.

It is worth noting that I then reinstalled all the fonts that I had just removed, and Chromium was not affected by them, this time: it works. Again, I don't know if the updates brought some fixes.

By the way, the integration between Chromium, snap and Ubuntu still requires some improvements.