This is what I did and it's working perfectly.
1. Boot to TWRP (cosmic)
2. Wipe everything and format data slot A and B.
3. Reboot to bootloader
4. Boot to TWRP (cosmic)
5. In slot A, install last build (installed in slot B)
6. Reboot to bootload...
I will leave here the steps I followed to have a perfectly running Mi A1 with LOS16.
1. Boot to TWRP
2. I did format data and wipe everything
3. Change slot
4. Boot TWRP
5. I did format data and wipe everything (why? I don't know, I don't really ...
I know other people got this error but is there any fix?
---------- Post added at 09:07 PM ---------- Previous post was at 08:37 PM ----------
I changed my username, that one sucked. Just to clear up any confusion before it happens
Ready to go: https://review.lineageos.org/#/c/LineageOS/android_vendor_lineage/+/206138/
It's almost done.
Any news about LOS 17, AmulyaX?
Also, is there any telegram channel to follow this development?