I have the same issue. Yesterday I installed an Ubuntu 20.04.1 on a new PC as I want to migrate to a different machine. After installing OpenHabian and installing Frontail it had the same layout issues.
I saw that the bootstrap.min.css file is in the folder /usr/lib/node_modules/frontail/web/assets/styles on my old machine and I copied it over to the new machine and now the layout looks ok. However I also noticed that the new machine is also lacking the files “dark.css” and “default.css” in this folder.
I am having the exact same problem - only openhab.css in the styles/ directory.
There are NO ERRORS in the web developer network view when it tries to load bootstrap.min.css. So I copied the url into another tab and it sure enough no error but redirects and loads frontail index, no error but not bootstrap.min.css. weird.
Frontail failed to install on a fresh openhabian 5.8-1. So I installed it manually. I am running frontail 4.9.1
are you on stable tree or on master of when you use the openhabian config menu ?
the stable tree expects a physical file bootstrap.min.css in the styles directory while the master tree uses an URL to load bootstrap.min.css from the internet.
I still have one issue with frontail since switching to master.
When I restart openhab “sudo service openhab2 restart” frontail takes ages to start as well.
I see the frontail icon in the OpenHAB UI selection instantly but it takes like 3-5 minutes after openHAB started until I can access the UI.
It happens to everyone, Frontail just takes time to start updating logs again after a OH restart. Perhaps someday it will get better but for now that is what we are stuck with.