Notes

I wanted to upgrade our VMware vCenter from 6.7 to 7.0 and ran into a problem, where the installation got stuck at 80%.

Luckily, I found this post, where the author had the exact same constellation:
https://www.ironcastle.net/vcenter-7-0-installation-stuck-at-80-waiting-for-rpm/

Yes, the ESXi host where the vCenter should be installed, had a free license. I changed to a trial license and the installation of vCenter did continue immediately.