Once it's night time in game, your Linoone will need to be level 35 or higher in order to evolve. If it's close, you may only need a couple battles or rare candies to get it to that point. Otherwise, level it first and then mess with the time of day. Enjoy the new Obstagoon.

How do you evolve Linoone into Obstagoon?

Galarian Linoone turns into Obstagoon if it is reaches level 35 or higher at night. No matter what time the Nintendo Switch's internal clock says it is, Pokemon Sword and Shield only count a Pokemon as evolving "at night" if it's actually night in the area a player is in-game.

Can normal Linoone evolve into Obstagoon?

This means that regular Hoenn Linoone can't evolve into Obstagoon, but the nature of the Galarian form allows it to achieve another evolution. Obstagoon is a Dark and Normal-type with the abilities, Reckless and Guts.