Authentication fails with prosody 0.11.2, but works with 0.9.12

The configuration explained in

https://github.com/jitsi/jicofo#secure-domain

works fine with prosody 0.9.12. Upgrading to prosody breaks it. Downgrading makes it work again. I did not change anything in the configs in between, but probably I should. Any idea, what the changes might be? (This is on Debian stable with/without backports.)

What exactly is not working?
There is a small change that needs to be done in the config for 0.11 this line should be storage = "none". Other than that it should work, except for jwt tokens, we are using 0.11 for the docker images.

This line is already in my config, it probably comes with your .deb package anyway.

What goes wrong:

After entering my username and password, I get:

Error
Oops! Something went wrong and we couldn't connect to
the conference: connection.otherError
                                         Cancel Retry

Now I see, that there is something in prosody.err, that does not occur with 0.9.12:

portmanager     error   Error binding encrypted port for https: No certificate present in SSL/TLS configuration for https port 5281

If this is the cause, how to solve it? I have LE certificates, and they are configured as here:
https://github.com/jitsi/jitsi-meet/blob/master/doc/debian/jitsi-meet-prosody/prosody.cfg.lua-jvb.example#L15

The error from prosody you can ignore, it is not relevant.
You have in your config storage = 'none'?

Yes. In fact in was storage = "null", but I tried now also storage = "none", but there’s no change in behaviour.

In the browser console, I get:

[conference.js] <e.value>:  CONFERENCE FAILED: conference.authenticationRequired
[JitsiMeetJS.js] <Object.getGlobalOnErrorHandler>:  UnhandledError: null Script: null Line: null Column: null StackTrace:  Error: Strophe: Server did not offer a supported authentication mechanism
at Object.i.Strophe.log (strophe.util.js:89)
at Object.error (strophe.js:2083)
at r.Connection._no_auth_received (strophe.js:3851)
at r.Connection._connect_cb (strophe.js:3940)
at e.Bosh._onRequestStateChange (strophe.js:5559)
[modules/xmpp/strophe.util.js] <Object.i.Strophe.log>:  Strophe: Server did not offer a supported authentication mechanism
[modules/UI/authentication/AuthHandler.js] <>:  authenticateAndUpgradeRole failed {connectionError: "connection.otherError", credentials: undefined, message: "no-auth-mech"}

Try adding consider_bosh_secure = true; to the general section of your prosody config. Does that change it?

You should also have this there: c2s_require_encryption = false

Now the error message changed! Again, after entering my credentials:

Error
Oops! Something went wrong and we could'nt connect to
the conference: connection.GET_SESSION_ID_ERROR
                                         Cancel Retry