The new and upgraded Framework Laptop

Used it for half a year. All works awesome, but I don't know how to update firmwares on my Linux Mint/Ubuntu. There are some guidelines on website, but they don't seem official, and say something like "you may need to fix your bootloader after" which sounds scary that I'll break my perfectly working system.

"The system" is on your hard, yes? Who's stopping you to buy another one for testing and swap them out? This way you preserve your perfect working system AND get to play with your desires on the other one. IMO framework laptop is made specifically to tinker with as much as possible in the end.