Exchange SE RTE has binary equivalency to Exchange 2019 CU15. It's just a licensing distinction. Allegedly.

I also had concerns and tested SolidCP with an Exchange SE server and I did not run across any issues. This was a cluster I joined to SolidCP management when it was running Exchange 2019 CU15. I ran a battery of tests (creating/modifying/removing Mailboxes, Users, Distribution Lists, Contacts, Disclaimers, etc.), upgraded to SE, and then ran the same battery of tests. I didn't run into any problems.