My thoughts/concerns so far

Your #1 is why I gave up on cryptomator. I was using it in conjunction with GoodSync, but it was way too slow and impractical for large numbers of files. I’ve tried every free and open source solution, including a few paid ones with encryption, like SyncBack and GoodSync. Overall, I decided on CrococryptMirror. It is free, fast and has sync built in. Does 256AES encryption, obfuscates file & folder names, and mounts encrypted volumes easily. The 2 downsides are there is no mobile version (not a big deal for me) and it uses Java Runtime, which has a memory leak, so after a day or two of sync activity, bloats memory usage over a gig, so you have to re-start crococryptor.

I’d like to see a better all-in-one solution that has:

  1. Cloud integration
  2. Sync built-in
  3. Encryption of files & file names
  4. Multi-destination sync (to local and cloud for same volumes
  5. Mountable backups
  6. Mobile access
  7. Open source code

Haven’t found anything that comprehensive yet.