I believe questions about running Bitcoin software on Ubuntu is as much on-topic as questions about running any other software on Ubuntu. But questions about the inner workings of Bitcoin and blockchain technology - not so much.
I agree with this comment.
Questions about using third party software on Ubuntu are on topic. Of course! But the question should be about using software on Ubuntu. This is a subtle matter. There is a bit of a grey area somewhere in here. Is the question really about using the software (the one you linked to is), or is it really about something else?
Eliah Kagan gave an example to help with this, which I call The Pirate Test:
"How do I put a footer on every page except the first in LibreOffice Writer" (on-topic) vs. "How do I write real-sounding dialogue between [...] the captain and first mate of a late 17th century buccaneer vessel in the short story I'm writing in LibreOffice Writer?" (off-topic).
You can try asking yourself, would an expert on this software (with knowledge of Ubuntu if necessary) be able to answer the question? If expertise in some other field (say, cryptocurrency, or 17th century English, or graphic design, or coding in Python) is called for, perhaps the question is off topic.
TL;DR: not everything about Bitcoin is on topic here, but using software relating to Bitcoin on Ubuntu is on topic.