It seems PatrickM managed to get it working (eventually) earlier in the thread, so at least I know it works on at least one other person's unit...
Do note that it does target 1.0.14, as that's the one image downloadable on the Xiaomi site one can recover to at the moment. I would encourage people to save themselves a copy. I don't think Xiaomi would be able to effectively stop downgrades/recovery to that image without flashing a new u-boot version with the image blacklisted, but I don't think they'd do that in the field as they haven't done it before.
I've been working on documenting the general process on the OpenWrt wiki and getting the RM2100/Redmi Router AC2100 into master in the meantime.
I think I messed up the article creation though.