Conversations cannot log in to ejabberd - error in stream

The ejabberd server I'm configuring has the following configuration for certfiles and for the port 5222. Gajim, Psi and Pidgin can connect fine. Conversations cannot. There's some stream error.

ejabberd's log shows

2021-07-15 16:15:01.459 [info] <0.381.0>@ejabberd_listener:accept:273 (<0.649.0>) Accepted connection 88.88.88.72:65069 -> 192.168.7.5:5222```

For Gajim, besides a line like the one above, it has two more when opening the connection:

2021-07-15 16:16:10.465 [info] <0.651.0>@ejabberd_c2s:process_auth_result:268 (tls|<0.651.0>) Accepted c2s SCRAM-SHA-256 authentication for test1@myserver by mnesia backend from 88.88.88.72
2021-07-15 16:16:10.550 [info] <0.651.0>@ejabberd_c2s:bind:442 (tls|<0.651.0>) Opened c2s session for test1@myserver/gajim.W2AAA7JO

Part of the ejabberd's config file is:

certfiles:
  - "/usr/local/etc/ejabberd/certs/myserver.pem"
  - "/usr/local/etc/ejabberd/certs/myserver.key"
listen:
  -
    port: 5222
    ip: "192.168.7.5"
    module: ejabberd_c2s
    max_stanza_size: 262144
    shaper: c2s_shaper
    access: c2s
    tls: true
    starttls: true
    starttls_required: true
    protocol_options:
        - "no_sslv2"
        - "no_sslv3"
        - "no_tlsv1"
        - "no_tlsv1_1"
    ciphers: "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256"
    dhfile:
      "/usr/local/etc/ejabberd/certs/c2s_dh2048.pem"

I've also tried commenting out the ciphers and no_ssl*, no_tls* but to no avail.

The ejabberd server is running not at the gateway but in a LAN location with port forwarding enabled.

What is wrong between Conversations and ejabberd?

tls: true
starttls: true

Those options are mutually exclusive. starttls is usually set at port 5222, and tls at port 5223.

And looking at the tls option documentation:

Enabling this option implicitly disables the starttls option.

So, you enabled tls on port 5222, which is a bad idea... together with starttls, which is another bad idea.

Simply, set tls to false or remove that line.