Posting this in case it helps someone avoid the issue I had.
Emby Server for MacOS 4.3.x requires MacOS 10.13 -- this is a change from Emby Server 4.2.x which could run on MacOS 10.12.
The release notes don't mention this (https://emby.media/c...er-43-released/)
Even worse, the Wiki lists the requirement as MacOS 10.6.3 (https://github.com/M...em-requirements)
This is disappointing as I'm not the first person to point this out but the release notes and Wiki haven't been updated. Consider this a friendly nudge to update the documentation accordingly.