I ended up just having someone else do it. I was able to use multiplayer mode for Make Bright the Arrows, Gather the Shields..., but that didn't work for Dehya's quest, and I got my brother to do that part.

There should be a category for getting the good ending (turning off the console as quickly as possible).

I'm not speedrunning, but it seems like the kind of thing you guys would know. I've tried the Omni-Ubiquiti Nets and they don't work on sumpter beasts. My last attempt at just killing everyone else resulted in the sumpter beast getting killed in the crossfire, and I don't want to try that again unless I know it works. I'm in step 10 of Make Bright the Arrows, Gather the Shields... (https://genshin-impact.fandom.com/wiki/Make_Bright_the_Arrows,_Gather_the_Shields...) and the wiki says it's just a Pyro and Geo skirmisher, but there's also a sumpter beast. Does anyone know some kind of glitch to keep the sumpter beast from spawning or to let me win without killing it? Or at least a good way to kill the skirmishers without it getting in the crossfire?

Edit: I killed the skirmishers without killing the sumpter beast. That didn't work. Maybe there's some trick to keep the sumpter beast from loading?