I use Coreboot + SeaBIOS with Qubes 4, and it works perfectly on a Thinkpad x230.
Any good how-to/doc you would recommend. I'm on a Lenovo T430 and might give coreboot a try...
Here are some of the guides I used. They're for the x230, but the x230 is similar enough to the t430 that a lot of stuff should be the same or similar. YMMV, though, as I'm currently struggling to get coreboot working on my T530
A video fully explaining coreboot for an x230:
https://vimeo.com/177951809
The coreboot wiki is the best resource, though it seems to be down as of this post.
https://www.coreboot.org/Board:lenovo/x230
This guide looks fairly informative for the T430:
https://github.com/sellerie98/Coreboot-ThinkPad-T430/wiki/Procedure
I strongly recommend buying a CH341A, some short jumper wires, and a pomona SOIC8 (5250) clip for this. A raspberry pi will work for flashing, but in my experience it is slow, and in some cases very unreliable, which could mean the difference between a laptop and a brick.
https://www.ibm.com/support/knowledgecenter/en/linuxonibm/liabw/liabwinstallusb.htm
sounds good when in doubt go with whats proven to work. Too bad as petitboot has nice features