This is what I have with my BBB on SDcard with Debian Buster:

root@arm:/etc/systemd/system# cat sshd.service
[Unit]
Description=OpenBSD Secure Shell server
Documentation=man:sshd(8) man:sshd_config(5)
After=network.target auditd.service
ConditionPathExists=!/etc/ssh/sshd_not_to_be_run

[Service]
EnvironmentFile=-/etc/default/ssh
ExecStartPre=/usr/sbin/sshd -t
ExecStart=/usr/sbin/sshd -D $SSHD_OPTS
ExecReload=/usr/sbin/sshd -t
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Restart=on-failure
RestartPreventExitStatus=255
Type=notify
RuntimeDirectory=sshd
RuntimeDirectoryMode=0755

[Install]
WantedBy=multi-user.target
Alias=sshd.service

root@arm:/etc/systemd/system# systemctl status sshd
● ssh.service - OpenBSD Secure Shell server
Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enab
Active: active (running) since Fri 2020-07-17 17:22:23 UTC; 22h ago
Docs: man:sshd(8)
man:sshd_config(5)
Process: 650 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
Main PID: 691 (sshd)
Tasks: 1 (limit: 1059)
Memory: 2.2M
CGroup: /system.slice/ssh.service
└─691 /usr/sbin/sshd -D

Jul 17 17:22:22 arm systemd[1]: Starting OpenBSD Secure Shell server...
Jul 17 17:22:23 arm sshd[691]: Server listening on 0.0.0.0 port 22.
Jul 17 17:22:23 arm sshd[691]: Server listening on :: port 22.
Jul 17 17:22:23 arm systemd[1]: Started OpenBSD Secure Shell server.
root@arm:/etc/systemd/system#

Works seamlessly. Just for comparison.

Best Regards,
Zoran
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