As far as who actually ends up with [the Darksaber]?
If Season 3 is the quest for Mandalor (to free or rule it?), I'm not really caught up with the cartoon cannon, Besides Bo, I think there is a Sabine character who has a claim to it, and even more factions out there, now including potentially the Armorer's clan, and "Vizla"? so there will likely be a fight.
I don't see Mando seeking to claim the throne, maybe helping free and/or unite his people seems more his drive, but not to claim power.
That doesn't seem like him.
The only reason he ended up with the Darksaber was to save the Yoby, he had no interest in power, or what the sabre symbolized or represented.
Even tried to willingly surrender it to Bo.
He might inadvertently lead people into action for a greater good, but that's a different kind of power. I think he walks from the throne, and leaves the rule to Bo or that Sabine character from the cartoons, or to any others in the mythology, and lets them have at it.
Clinging to the Darksaber (and everything it "offers" ) might ultimately bring death, Mando likely sees it's time to let it go!
Bo might be in a rough spot, if she can't....
Something else other than a symbol, or a dogmatic "way" is going to have to unite them, or they will destroy each-other.
Mando likely helps them see (or remember) that, or leaves their fate to them.
Final trope is I imagine - (Red Harvest/Yojimbo/Fist Full)- Poisonville is "cleansed" it's own people left to rule themselves,
he walks off into the sunset to continue his wandering - cue his badass theme music.