You should check out the work done by Kaze Emanuar. He's made a number of demakes, new maps, new games, and much more in Mario 64

https://mario64hacks.fandom.com/wiki/Kaze_Emanuar https://www.youtube.com/user/KazeBG0

Decomp modding is the next unexplored frontier in SM64 modding. Kaze (the figurehead of the community) uses decomp ever since SM64 Splitscreen, and with brand new features being added by more technical users, there's a ton of cool mods being developed, such as:

-Golden Sun 64, complete with a random encounter battle system: https://www.youtube.com/watch?v=zdHEwTVCoo0

-SM64DS minigame Wanted in SM64: https://www.youtube.com/watch?v=BqjISz_wW7E

-Princess Peach Sex Hack (All I can say here is, don't be fooled by the name): https://www.youtube.com/watch?v=5dMn3LgYF4c

There is a somewhat active community, including a model exporter for Blender (which exports Blender models to the format that Super Mario 64 uses). New maps, too.

I haven't seen any total conversions.