Had a very scary moment there, thought i had bricked my switch.
My switch was still on FW 7.0.1 ( was using hekate 4.10.1 and atmo 0.8.9 already tho) and i thought it was time for an update for the faster laod times in Zelda/Mario. So i went online and into system settings to hit that update button.
Update downloaded, installed, switch rebooted into hekate into atmosphere, and... the console froze on the Switch logo. After a hard shutfown and reboot, the console was still stuck on the Switch logo.
So i went and removed all custom sys modules and stuff from the SD card and booted pure hekate + atmo.
Still froze on boot-up during the logo. This is where i sorta started to panic, thinking "THE ONE TIME YOU DON'T DO A NAND UPDATE BEFORE UPDATING, FUUUUUU"
Eventually i had to boot stock firmware through hekate (had to find an up-to-date custom warmboot and secmon on the internet first, thanks 7.x+) to get the switch to go past the Switch logo and boot into the OS. Giant load off my shoulders that it still booted at all.
I then checked to see if atmosphere booted at all, and launched it through fusee-primary instead of hekate. It works!
Curiously, i then went back to launch atmosphere through hekate like i did earlier, and now it suddenly works again whereas earlier it jsut froze. Completely the same setup and everything, nothing changed.
There was probably something during the update process from 7.0.1 to 8.0.1 that didn't work on atmosphere, and that booting stock through hekate resolved? Might be worth looking into, but i don't know how reproducable that is.
Well if someone else has that problem, that's one way to resolve it i guess.