I decided to try out the Gutenberg editor, but I ran into an issue with my service posts. I couldn’t see a way to set the speakers and service topics in the new editor. This isn’t a showstopper yet because we can still use the classic editor. But it would be nice to get it resolved before Gutenberg becomes the default in WordPress 5. BTW, the service date and time fields are enterable/editable on the service page, so that part is fine.
We haven’t yet tested the theme with Gutenberg.