Same here. Waiting for new release.
Get:5 file:/var/cache/openmediavault/archives Translation-cs
Ign:5 file:/var/cache/openmediavault/archives Translation-cs
Get:6 file:/var/cache/openmediavault/archives Translation-en_GB
Ign:6 file:/var/cache/openmediavault/archives Translation-en_GB
Hit:7 http://httpredir.debian.org/debian bullseye-backports InRelease
Hit:8 http://deb.debian.org/debian bullseye InRelease
Hit:9 http://deb.debian.org/debian bullseye-updates InRelease
Get:10 http://download.onlyoffice.com/repo/debian squeeze InRelease [10.7 kB]
Hit:11 http://security.debian.org/debian-security bullseye-security InRelease
Hit:12 http://packages.openmediavault.org/public shaitan InRelease
Hit:13 https://openmediavault-plugin-developers.github.io/packages/debian shaitan InRelease
Hit:14 https://download.docker.com/linux/debian bullseye InRelease
Hit:15 https://openmediavault.github.io/packages shaitan InRelease
Err:10 http://download.onlyoffice.com/repo/debian squeeze InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8320CA65CB2DE8E5
Reading package lists... Done
W: GPG error: http://download.onlyoffice.com/repo/debian squeeze InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8320CA65CB2DE8E5
E: The repository 'http://download.onlyoffice.com/repo/debian squeeze InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.