I get your point. At some point this widget provided an option to specify the backend command manually, though I removed it because I couldn't see any use cases. I would happily add this functionality again if you require it.
I have my solution and I think many others have their own. In my opinion it's perfectly fine to just state "platforms that don't have the necessary packages in their system package manager aren't supported, use at your own peril" so niche distributions making up the long tail of your users don't end up taking unreasonable amount of support and development time.