When trying to change the settings of the outgoing SMTP server, nothing happens when trying to submit them. The only way to close the dialog is to go back, which causes the changes to be lost.
Performing the same action for the incoming server works as expected — it attempts to connect to the server and asks whether to accept the server certificate.
This issue occurs both on a fresh installation, when importing settings from desktop Thunderbird, and on an installation where the server has already been configured.
Version 11.1 + 13.0
WORKAROUND: seems to be triggered by using a no-authentication account. After switching to plain-text auth, entering some dummy credentials and reverting back to no-auth, the settings can be submitted.