Not saying it isn’t a mess, but once you know what you need, it feels no harder than normal. Regarding the 10k other boards, well, that’s how QMK from source always is. You just make a shortcut to the folder for the keyboard(s) you’re working on & you never see the rest.
The firmware version that’s shipping still looks to be v0.2.9, so:
clone -b v0.2.9 https://github.com/FrameworkComputer/qmk_firmware.git
Custom QMK firmware? - #14 by MJ1
Clear eeprom step: Custom QMK firmware? - #31 by MJ1