Interesting. I have one Librem 5 on which I installed Mobian, just to have a preview of what will come to PureOS eventually, app and Phosh wise, but for me Mobian is by far not as robust and reliable as PureOS Crimson.
My current point of view is that PureOS should catch up as close to Debian as possible, ideally Debian (Mobian) should run well on the Librem 5. Purism is upstreaming a lot of improvements, which is great.
However, even when PureOS is up-to-date with Debian releases, I think PureOS will probably be “better” than Debian (Mobian) because PureOS will probably be the distribution where Librem 5 specific patches and improvements land first. Maybe there will also be some patches that for some reason cannot be upstreamed.
Also, I like having bleeding edge software and see improvements early. But for a phone this conflicts with the requirement that it should be very stable and robust. Maybe there could be something like a PureOS Unstable for people willing to accept some risk, or people with more than one Librem 5.
Related to this is the fact that I’m often a bit in doubt where to report an issue with an application, or Phosh. Because the PureOS versions of Posh and many applications are not up to date with their newest releases, I’m reluctant to report issues upstream because I do not know if they already have been solved. But also I do not want to put extra burden on the Purism team by reporting issues that might have been fixed upstream.
To address this, I thought that installing Mobian on a separate Librem 5 was a good idea, because it is more current with Phosh and many applications. If an issue is in Mobian, I could report it there, or to the application project, without the “risk” to report issues that have already been solved but are still in older versions distributed with PureOS.
And if Debian, Mobian and PureOS would be all very similar, improvements and fixes upstream in applications and Phosh would arrive in PureOS quickly.
I prefer to see a healthy collaboration between Mobian en PureOS, maybe where PureOS would focus on Purism device specific development, like the kernel, and Mobian more on the mobile Linux platform as a whole, base on Debian.
See also: PureOS Optional Subscription Added to Advance Development - #26 by guido.gunther
And I in my opinion the PureOS Crimson release was a big step towards bringing PureOS, Debian and Mobian closer together. Which is good for all or them, and also for the mobile Linux eco system in general. Also made possible by all people who have a totally optional PureOS subscription to further the development of PureOS, and so indirectly also the mobile Linux as a whole.