So far there have only been 2(!) opportunities iirc to evolve Mons into their regional counterparts. Once in mid 2022 (Exeggcute→Alolan Exeggutor) and then in 2024 (Koffin→ Galarian Weezing).
Why are you so stingy with us getting Regional Forms, on our own, Niantic‽
by Die4Gesichter