Mi Mix 2 Chiron on R .18 update attempt to 21 resulted in "can’t load Android system. Your data may be corrupt… "
Then suggests formatting my device.
Help! Can I buy a vowel please??
Regain your privacy! Adopt /e/ the unGoogled mobile OS and online services
Booting to TWRP recovery, you should be able to copy /sdcard content (your files) to a computer using MTP.
If your phone was encrypted and TWRP is not asking for password/scheme, unfortunately you can’t backup /data.
If not encrypted or decrypted after asking for a password/scheme, then you may try to take a TWRP backup ([HOWTO] Backup and Restore Data on Android Devices).
However, please be aware that restoring parts of /data (like contacts, SMS, …) is very time-consuming and painful 
You may try to go back to 0.18 at a first step : push the ROM image to /sdcard, then use TWRP Install button …
Thank you for your reply! I’m actually in e recovery as I thought it was necessary to apply the update. I’m not sure I see how to access storage the Orange fox recovery zip so I can reapply it… enabling adb option from within e recovery doesnt allow me access. Says unable to access MTP device “003,013”. If thats any clue. Also, I removed PW and fingerprints prior to attempting to update but believe I was encrypted. The e recovery page says I’m on 21, as well…
Sorry, I only know about TWRP for this device …
FYI, I successfully applied 0.22-r over 0.18-r today, after disabling Screen Lock (was pattern for me) and rebooting again to system.
If you can’t enable MTP, you can try to “adb pull /sdcard C:\MyBackup” or “adb pull /sdcard ~/MyBackup”.
Thank you for following up, I’ll give that a shot. --Eh didn’t work… “/sdcard/: 0 files pulled” is my report.
Btw, I had Magisk installed as well, is that where I goofed? Btw, there is a magisk module twrp-helper that enables internal storage in backups(now I remember) as well as an A/B retention script as well that may be of interest to the thread you linked.
Guess I’ll try to fastboot flash twrp or OF recovery and check for love there. Both are much more feature rich than e recovery… brb
Magisk may cause trouble with updating, yes 
If you kept your original boot image, it may worth a try to put it back.
Also, it seems that your current recovery didn’t mount /sdcard, or it’s damaged …
You may try to boot TWRP without installing it, using fastboot boot TWRP.img (replace TWRP.img with path for TWRP image file on your computer).
thanks again, I’ll try this…