This is almost completely broken on non-GCF (Google Services) phones. I've seen message notifications arriving 12 hours (!!!) later.

For those users it's recommended to use Matrix clients alongside something like https://ntfy.sh/ , which sends push messages to your phone. However, one could then also ask: What is the need for Matrix in that case? I suppose end-to-end encryption would be one argument, but you could also encrypt message (contents) client side with something like GPG. So, I'm left wondering what really is the benefit of Matrix for those users.