Quick answer
Where you can play now
Fields of Mistria 1.0 is available on PC through Steam. The team is focused on the PC release and may evaluate console ports later. No Switch or Switch 2 release date has been announced.
Switch and Switch 2
There is no separate release date for either console yet.
What to use for the PC version
PC players can get the game through Steam. Use the game website and Steam page for the latest store and platform details.