Hi,

As you can see sendmail used to be working:

$ nextcloud.occ config:list | grep mail
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
            "emailTestSuccessful": "1",

Now it is not selectable in basic settings and does not work anymore.
I assume it vanished in some upgrade.
Does one nowerdays need to install some dependency?
sendmail (provided by postfix) is still available on the system.

Best
Andreas