Uninstall Exchange Server after non hybrid migration

Hi all,

I work for an MSP where we already migrated a few customers to exchange online.

For that we never use entra id connect to sync the users because most of the times, the customers are to small and for example in a dental office they mostly have 1 user which is logged on every computer at the registration. The doctors mostly have their own users.

For that we create users manually or sometimes bulk in entra and then give them the license, most of the times its exchange plan 1.

So my question: after I migrated all mailboxes to exchange online and everything is working fine, what do I do with the exchange server ? My boss just turn the VM off and deactivate the startup on the hyper V host.
What is the proper way in this situation? I barely have experience in exchange servers.