Old removed E2010 server preventing install of E2019 Management Tools for hybrid recipient management

New to me environment using M365 with hybrid identity (Entra Connect) but no hybrid mail flow.

Sometime in 2019-2020 email was oved to M365, but no details are available to me on how that was accomplished, only what I can discover myself. During the move to M365, there was an E2010 server that was removed from the environment. An uninstall of Exchange was not performed.

Existing staff has been managing recipients in AD via an unsupported fashion. Users are created in ADUC, sync to Entra, and licensed. Manually editing on things like proxyAddresses and msExchHideFromAddressLists is being done. While this works, I want to convert to supported behavior of managing recipients with Exchange Mangement Tools.

When I try to install management toolsf rom 2019 CU14, I get a pre-req check error for "All Exchange 2010 servers in the organization must be upgraded to Exchange 2013 Cumulative Update 21 or Exchange Server 2016 CU11".

What's the correct path I should take to get to where I need to be given that I' just looking for management tools, and not to have a fully functioning Exchange server.