I only have experience with 2 sites (in different countries), but 20 site or more should be possible. The exchange of database information is probably not the problem. Synchronising all the files between so many sites could be a problem. You will need a fast connection between the sites to synchronise all files.
Regards, Martin
Regards,
Martin van den Berg
NKM Noell Special Cranes GmbH
Inventor Professional 2019.3 + Vault Professional 2019.1.1