Firefox on ChromeOS won't start after install
I've tried to install the desktop version of Firefox on my brother's new Chromebook, using the instructions here: https://support.mozilla.org/en-US/kb/run-firefox-chromeos I enabled Linux, installed Flatpak, and installed Firefox. But when clicking the Firefox button nothing happens, a circle on the program icon just keeps rotating endlessly. When in the terminal, using the command flatpak run org.mozilla.firefox (which I got from https://flathub.org/apps/details/org.mozilla.firefox ) I get the following error message: bwrap: Can't mount proc on /newroot/proc: Operation not permitted error: ldconfig failed, exit status 256
I also followed the guide here: https://techpp.com/2021/12/02/install-firefox-on-chromebook/ which is a slight variation of the same procedure, but the same thing happens (circle on icon, error message in terminal).
Did I do something wrong? Is this an error with Flatpak?