I like what Bohemia Interactive did with Mini DayZ, making a still very fun game that captures most of the experience of the Desktop game but in an easier to access form.
If Valheim were ported into an isometric, topdown, or sidescroll 2D format, the controls could probably be simplified into onscreen controls of a single dpad or psuedo stick and maybe 4 buttons (What I'm thinking is 1 dedicated equip button, and then 3 that can be switched by it to do dodge, block, and attack if weapons drawn, and pick up / withdraw, drop / deposit, general use when not equip).
Such a thing might somewhat resemble Terraria, but be a bit more straightforward.
Idk if IronGate is interested in mobile development, but since the PC game is nearing completion, it'd be something they could do that wouldn't require thinking up a whole new universe and design ideas.
I would purchase it if it were made.
Source: https://www.reddit.com/r/valheim/comments/tbahp3/valheim_mobile/