Thanks mnalis for posting the fix on the Github issue thread. I had spent time fruitlessly trying the Nextcloud app settings, permissions settings, and other stuff, but nothing had any effect - auto upload would not trigger.

Under Android Settings / User & accounts / Nextcloud / Sync the options File sync was OFF! I toggled it ON and the thing started uploading photos immediately.

At least not reliably. What is going on?
I can see new messages in other IMAP clients, such as K9 Mail. But Thunderbird shows no new messages, despite F5 or Shift+F5.

TB never behaved this way before (102). New messages were automatically fetched.

Going offline by clicking the icon in the lower left makes TB prompt if we first want to download all messages; the blue list in the status bar keeps pulsing forever, but no new messages are fetched.

Restarted into "troubleshoot mode" - now it works. Ok, so could it be a problem with one of my extensions?

Seems not - I restarted Thunderbird with all extensions disabled, and it still will not fetch any messages from any email account. I have no time for this. I am reverting to v102 from my profile backup (always good to have a backup of your profile!).

• https://support.mozilla.org/en-US/questions/1425745
• https://support.mozilla.org/en-US/questions/1425572

The libpoppler-utils package contains the tool pdfsig that does just this.

$ apt install libpoppler-utils
$ pdfsig file.pdf
Internal Error (0): couldn't find default Firefox Folder
Digital Signature Info of: file.pdf
Signature #1:
  - Signer Certificate Common Name: Donald Duck
  - Signer full Distinguished Name: C=SE,E=donald.duck@stackoverflow.com,O=Uppsala universitet,CN=Donald Duck
  - Signing Time: Oct 10 2021 15:12:20
  - Signing Hash Algorithm: SHA-256
  - Signature Type: adbe.pkcs7.detached
  - Signed Ranges: [0 - 132117], [137169 - 143786]
  - Total document signed
  - Signature Validation: Signature is Valid.
  - Certificate Validation: Certificate issuer is unknown.

The complaint about Firefox folder goes away if you simply create the empty folder ~/.mozilla/firefox.

• https://stackoverflow.com/questions/41301138/how-to-check-if-a-pdf-has-any-kind-of-digital-signature/67331180
• https://askubuntu.com/questions/226257/how-can-i-validate-a-pdfs-digital-signature-with-evince
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=926404
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=924050