We released our updated installers for BIMcloud v21 which are available from their original download links.
Upgrade process of BIMcloud v20 Server to BIMcloud v21 Server will fail on macOS 10.13 with the following error message:
Your BIMcloud v20 Server will remain in its current configuration. An updated installer for BIMcloud v21 will be released in the near future. If possible delay the upgrading of your macOS until an updated BIMcloud installer is available.