In this specific case, no evolution stone, no level of friendship or even an item to hold... To make Galarian Farfetch’d evolve to Sirfetch’d, you will have to succeed in a kind of mission in the middle of a battle!
Get 3 Critical Hits in 1 Battle
This seems very difficult but it is feasible because Galarian Farfetch’d holds a Leek (an object that increases his chances of making Crit). Be careful, it is possible that the Galarian Farfetch’d you catch does not have one. Just try to find another one.
To try to succeed in the evolution condition, find a Trainer of your level, with 6 Pokémon if possible (to make the fight last) and of course to heal your Galarian Farfetch’d all along so that only he can fight.
The most important thing is to make the battle last.
Where to find Galarian Farfetch’d?
Be careful, this is a Pokémon exclusive to the Sword version. You can find it in the tall grass, with a very rare spawn rate:
- Route 5
- Giant's Mirror (Wild Area)