hi! FYI, if you don't get responses in this sub, you might try /r/linguistics - they have a stickied post for quick questions
Å was introduced in 1948. The use of aa in lieu of å is seen mostly in personal names, some Danish geographical names, and in transliterations where å is unavailable.
I've been looking for something on Ø, but I can't find anything so far. Like /u/Searocksandtrees mentioned, perhaps try /r/linguistics?