I haven't had occasion to spin-up Exchange SE yet, but I've read plenty of descriptions of other admins running it. I have no reason to believe Exchange itself relies on any centralized features. "New Outlook" has been alleged to use centralized servers even when connected to an on-prem Exchange SE install, and given that it's "modern" MSFT software that wouldn't surprise me, but anybody stupid enough to use "new Outlook" gets what they deserve.