You don't have to - you can use an Android Emulator. But it will suck.

If you don't like it, it's not very hard to make Genshin single-player only. Most of the game is client-side, except for the spawning of enemies and resources. If you can figure out how to replicate it, you can get a 100% server-less Genshin Impact. I can definitely help with that if you want.

People have tried in the past to get the game running in single-player mode, and managed to get everything working except for mob spawns.

You'd also need to figure out some progression system to unlock characters, but that's not too hard.

If we could find some people to maintain the patch I'd be very willing to contribute to this too.