Bug#990069: openssh-server: Not accepting new connections during Debian 10 -> 11 upgrade

Package: openssh-server
Version: 1:8.4p1-5
Severity: normal

Dear Maintainer,

During a Debian 10 -> 11 upgrade, the SSH server doesn't appear to be accepting new connections. IMO this is less than optimal, and not sure if this was always the case.
Would it be possible to keep accepting connections, or at least to make the time window in which SSH is down as short as possible?

Greetings,

Olaf

-- System Information:
Debian Release: 11.0
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-16-amd64 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages openssh-server depends on:
ii  adduser                3.118
ii  debconf [debconf-2.0]  1.5.71
ii  dpkg                   1.19.7
ii  libaudit1              1:2.8.4-3
iu  libc6                  2.31-12
ii  libcom-err2            1.44.5-1+deb10u3
ii  libcrypt1              1:4.4.18-4
ii  libgssapi-krb5-2       1.17-3+deb10u1
ii  libkrb5-3              1.17-3+deb10u1
ii  libpam-modules         1.3.1-5
ii  libpam-runtime         1.3.1-5
ii  libpam0g               1.3.1-5
ii  libselinux1            3.1-3
ii  libssl1.1              1.1.1d-0+deb10u6
ii  libsystemd0            241-7~deb10u7
ii  libwrap0               7.6.q-28
ii  lsb-base               10.2019051400
iu  openssh-client         1:8.4p1-5
iu  openssh-sftp-server    1:8.4p1-5
ii  procps                 2:3.3.15-2
iu  runit-helper           2.10.3
ii  ucf                    3.0038+nmu1
ii  zlib1g                 1:1.2.11.dfsg-1

Versions of packages openssh-server recommends:
ii  libpam-systemd [logind]  241-7~deb10u7
ii  ncurses-term             6.1+20181013-2+deb10u2
ii  xauth                    1:1.0.10-1

Versions of packages openssh-server suggests:
pn  molly-guard   <none>
pn  monkeysphere  <none>
pn  ssh-askpass   <none>
pn  ufw           <none>

-- debconf information:
  openssh-server/permit-root-login: true
  openssh-server/password-authentication: true