When trying to start Chromium, it just silently quits (a short flash of a window, but too short to see anything).
When running from konsole:
flatpak run org.chromiumChromium, then the following error shows:
[0827/110642.679777:ERROR:scoped_ptrace_attach.cc(27)] ptrace: Operation not permitted (1)
You can’t install it from a non-deb repo? Would be helpful for those trying to help you for you to actually post what OS you are running, cause otherwise we are just guessing and wasting our time. I for example run a Arch based distro so I just grab Chromium from the extra repo.