@padraic Definitely not my work. Anyway, you can check GitLab to see who worked on this: https://gitlab.com/debclick/uFirefox 😉

Firefox has been packaged with click already https://gitlab.com/debclick/uFirefox/. Last commit was 4 months ago and it works. There are some minor issues, (with workarounds), like keyboard sometimes not opening, and to scroll by touch you have to install the "scroll anywhere" extension.

@padraic What is the installer on the PC doing?

The following desktop apps are working ok in OTA12 via Libertine in my tests (meaning that they launch and can, with some work arounds and patience with the clunkiness of their guis when used on mobile devices, generally made to function), and all offer some amount of functionality that is not necessarily already found with UT native apps.
For apps that much more suited for desktop, like AbiWord and GIMP, I would suggest using them with an external keyboard/mouse/trackpad and/or external display.

abiword - word processor
file-roller - archive manager
evince - pdf viewer
firefox - web browser
gimp - image editor
gthumb - image gallery & editor
gedit - text editor
medit - text editor
gtick - metronome for musicians
youtube-dl - command line YouTube video downloader - run in Terminal app
hardinfo - system information & benchmark tester
xournal - note taking via touch, stylus or text; pdf annotator
mypaint - illustration - note it is somewhat laggy and crash prone though
easytag - id3 tag editor for audio files
p7zip-full - command line archive manager for 7zip files
p7zip-rar' - command line archive manager for rar files
mpv - media player - open files into it from the File Manager app

Best regards,
Steve Berson

This has worked for numerous users: https://forums.ubports.com/post/13645.

I've found running these commands works more reliably from fastboot mode.