I'm telling y'all I had the exact same problem. Partitions were missing, couldn't mount or do anything without errors.
Then somehow, following the steps I listed on page one and doing a hard reset at just the right moment in the bootloop then WHAM the partitions were back. There did seem to be a couple files missing but I was able to do a dirty reinstall of the ROM I was using from the source in my download folder after the partitions reappeared and bam, I was back in business.
Now clearly what I was dealing with must have been a software issue and not a hardware problem, or at least not a permanent one but for anybody finds themselves with this issue its def worth a shot. A lot easier than going through unbrick process plus u don't gotta reconfigure everythingb or restore your files