I was thinking about Matrix too! I was also considering going back to old-school IRC, or maybe using a P2P platform to cut out all reliance on servers.
I'd kinda love to see IRC get a 21st century makeover. I like it's simplicity, but it is missing some things that are just too useful to give up.
The simple ability to be offline and then fire up your discord or matrix client and not have missed out on any conversation, whereas with IRC if you go offline and discussion or messages during that time are lost to you. But I miss the IRC vibe.
I used to run a Rizon IRC server before Discord came about - #sissyology. I'd love to restart it again.
I think the way I dealt with the issues were a combination of scheduling chats at certain times, as well as keeping an app running in the background on my phone so I didn't miss out on chatting.