I'm considering doing a hunt for Magnezone and potentially Garchomp in the future so I need to know how many and where they are. If you could provide a map with where the fixed spawns are, that would be great.
There are 10 Magnazone encounters along with 10 Garchomp encounters. they are both dotted around the rim of The Great Crater at random intervals however there are 2 spots in particular that would be good for shiny hunting, first on the south-west corner of the map there are 2 Mangazone spawns relatively close to each other. and with Garchomp there is one spawn directly north of the Academy and another next to it.
Source; https://game8.co/games/Pokemon-Scarlet-Violet/archives/369146