Yes, just create an empty room with only you inside

Couldn’t you use HMAC with shared secret key to authenticate messages while keeping plausible deniability? Since the key is only supposed to be known to the 2 parties, the recipient can deduce that a message was actually sent by the sender if he did not create it himself. I think that’s what OTR was using.

Gocryptfs or CryFS. Many GUI available (Vaults, SiriKali, Plasma Vaults). Android compatibility with DroidFS.

DroidFS does not have Internet permission so any data exfiltration is prevented at the OS level.

To type with only one finger, there’s 8Vim.

:help i_CTRL-H

 or CTRL-H  Delete the character before the cursor (see i_backspacing                                                       about joining lines).

From a security point of view, it’s better to create a dedicated network for each of your containers, as apps won’t be able to communicate with each others directly.

You can even not setup networking at all and use UNIX sockets instead. However, back-end apps will need to support that.

Check that the certificate store of your device is up-to-date. Ensure it is also set to the correct date. If all is ok, check that your device resolves your domain to the right IP. If it’s correct, check that the certificate fingerprint you get from your device is the same as what you get from your working devices.

If all looks good, maybe you can provide the exact error by attaching the output of curl -v or openssl verify.

What about DroidFS?