What homebrew alternatives to Vancian casting in PF2 already exist?

I hate, absolutely despise, Vancian casting. I'm not here to discuss why, and neither care to hear arguments in its favor, I've already had this talk before. Sadly, this archaic magic system wasn't one of the things Paizo got rid of when writing PF2, and the game was balanced with it in mind. I want to know what homebrew alternatives to magic systems already exist, that I could use in place of the existent one, and if these homebrews do a good job in keeping the game balanced. Thank you in advance.

EDIT: I see a lot of people mentioning spontaneous casting or flexible spellcasting. But I'm talking about the usage of spell slots as a whole.