All Secrets

[Jane Doe]

Played the game on switch but came here to ask for help because I‘m totally in love with this game and also a completionist, and I couldn‘t find anything on the web regarding this.

Is there a list of all secrets there are in the game somewhere?

By ‚secrets‘ I mean game content or items which don’t have an achievement or quest leading to it.
What I have found so far is:
- award mask in homelanda
- hidden room in kiiruberg
- crown in basto
- beret in basto
- the real tato king in basto

Did I find them all?
Also, does the Ursa Major star constellation (looking through the telescope in Kiiruberg) lead to anything or is it just a little easter egg?

Any help would be appreciated!