Microsoft Planner is included in most Microsoft 365 plans. Pretty much if you've got Teams, you've got Planner (and you can just add Planner as Tab in a Teams channel). At this point it has surprising feature parity with Trello.
Last time I checked (a few months ago), Planner still could not be backed up. Like, at all. If someone went in and deleted a whole bucket you can't recover it, not natively, and not with third party. So that's a big fat no from me.
I seem to recall dumping Planner to JSON easily enough. I don't know if you can easily restore directly from its JSON, but the JSON was nice enough to work on for what little I needed to do with it.
My current employer shut off Trello and forced us over to Jira and is threatening to disable Planner, so I'm "not allowed" to rely on Planner enough day-to-day so it's possible it is either better or worse than I remember it being in that department. But this Jira outage has me reevaluating, and they haven't turned off Planner yet.
