- Latest version, updates for Pop_OS as of the date/time of this post, Feb 18, 2024. Using Gnome, not System76 Cosmic.
- Was running previous version of Fopnu (not a fresh installation).
- Using Eddy for upgrade.
Eddy reported installation failure (Child process exited with code 100).
I verified the integrity of my download (64 bit .deb).
I verified apt reported no unmet or broken package dependencies. No updates or upgrades pending, --fix-broken, clean, so forth, dpkg, too. All OK.
I saw no other reports of such a problem - it's my machine, not you or yours!
Resolution:
I simply installed Fopnu manually, as you thoughtfully provide. That works fine, thanks very much.
Only, I wish to report this problem and resolution for your or anyone else's benefit.