Did you even notice that you typed this all on a single block?
Very confusing, difficult to read, difficult to understand, and with no relevant system information.
inxi --admin --verbosity=8 --filter --no-host --width
open files using an alternate program through Dolphin.
You mean ‘open with…’ does not appear in Dolphin for a context click.
It should show ‘Open with Okular’ and ‘Open with…’ as top two options if you had KDE Plasma installed…
But you didn’t say. Neither did you say if you tried this on a fresh USER account.
Could not find the "keditfiletype" executable in PATH
Sounds like Dolphin isn’t running on Plasma, or it’s in some non-standard environment where keditfiletye or kde-cli-tools isn’t exposed to Dolphin.
This is a mess - need more information I think.