Hi all,
I found the issue. I had another Horizon installation on vSphere 6.7 + vSAN and got the same error, the customization stuck and timet out.
I checked the composer logs and there was an issue with mounting / writing the personality disk (20MB).
I configured the golden image with an nvme controller and that wasnt correct, I replaced the nvme controller with an paravirtual and now its working 
Same problem was on my vSphere 7 environment, replaced the scsi controller and everything is fine.
Its strange because the nvme controller is the default controller for windows vms on vsphere 7 
I hope it will be fixed or supported soon.
best regards
Sebastian