My experience and what's still missing
I installed Ubuntu Touch on a Poco X3 and used it as my everyday device for about two weeks.
Of course, I encountered various difficulties, which I would like to list here: (Note: I usually use a Graphene OS phone).
list itemThere is no clean integration with cloud solutions: Nextcloud works to some extent, but all areas should be able to be docked to the supplied apps: mail, calendar, and contacts.
Ideally, a secure cloud such as “Proton” or “Infomaniak” would also be provided.
list itemTo get around this problem, one alternative would be to use a cloud like Proton directly in the browser. That's what I do on my Linux PC.
For this to work properly, the browser on the desktop and on the cell phone would have to be the same. And then it would also have to be possible to synchronize the settings (Vivaldi browser). That way, you could work without an app.
list itemOf course, banking apps won't work, but you'll have to live with that if you change your processes a little.
list itemYou can't expect the same convenience as with an Android phone. I think back to when I switched from Windows to Linux. It was a shock at first, but today I can't imagine anything else.