VRA deployments fail: VIB has no signature

I just finished a fresh install of ZVM 8.5 on Windows 2019. ZVM is connected to a vCenter (6.7U3) with many ESXi hosts (also 6.7U3), and to vCloud Director (10.1.1).

Now I’m trying to deploy the VRA’s, but run into a problem. The deployment fails on several hosts.

The ZVM reports:

VRA installation IP=10.x.x.x. Failed: an error has occurred during vib ‘SshKeyAppendVib’ installation.

In the eventlog of each host I found the following error:
Could not stage image profile ‘xxxxxxxxxxx’: (‘Zerto_bootbank_SshKeyAppendVib_1.0.0-0.0.1’, “(‘Zerto_bootbank_SshKeyAppendVib_1.0.0-0.0.1’, ‘The VIB Zerto_bootbank_SshKeyAppendVib_1.0.0-0.0.1 does not contain a signature.’)”)

Error “vib SSHKeyAppendVib” when Attempting to Install a VRA

Dit KB-article offers no solution to me, because none of the hosts appear to have a ‘/mnt’ mount:

[root@xxxxxxxxxxx:~] ls /mnt
ls: /mnt: No such file or directory

I can’t find any reference to this issue on the internet, except for some references to the Host Image Profile Acceptance Level, UEFI Secure boot and the Advanced System Setting VMkernel.Boot.execInstalledOnly. However, these things are all identical on all hosts (I checked).

Any thoughts?