I was able to to flash a custom rom with the suzyq cable thanks to MrChromebox’s advise here: Flashrom error when trying to unbrick with SuzyQ - #2 by MrChromebox
I didn’t try it but I also found a copy of the gcstool here https://files.tree123.org/utils/x86_64/gnu/gsctool
So I’m g2g now. Thank you MrChromebox for this amazing project. I’ve used it now on 3 chrome{book,box} devices.