Thanks for the feedback.
Regarding the Learn-mechanic: This has been asked
previously and we weren't interested in at that time to change the rules and introducing sideboards into Highlander. Mind that this is also in line with other formats without sideboards. See
https://twitter.com/wizards_magic/status/1375151063020359685?lang=en and
https://mtgcommander.net/index.php/2021/04/12/2021-april-update-strixhaven/As for Dungeons: Based on
what is known now of the mechanic, I don't see a reason why Dungeons couldn't be used. The key phrase here is this from that linked video:
"Now Dungeons. They don't go into the deck. You can keep them in your sideboard, but, and this is important, they don't take sideboard slots. You just have access to them. And you bring them in to the game when you venture into the dungeon."Commander, where sideboards are also not permitted, has landed into similar conclusions:
https://www.reddit.com/r/magicTCG/comments/o7220z/sheldon_confirms_dungeons_are_commander_legal/I hope you are considering this idea and disuss it.
I'll make sure there's an announcement regarding this, and while waiting for the official rules on Dungeons, I opened a discussion point on this on the council boards. They'll chime in on there, if not here.
What I said above, is just my personal opinion.