I like what Discourse represents. I however have also noted the impact of mobile messaging apps. Telegram in this case.
I am not a developer, and neither am I quite well versed on some things, but I know what a good thing looks like. And I think outside of email, someone would take up on a plugin to fetch summaries of interesting forum topics and push to Telegram bots. Someone has implemented that quite well and we use it for Telegram channels, to alert channel members on things they want to stay connected to.
This may perform better than an app IMO. My team decided again’st developing and maintaining an app and a Telegram channel comes in quite handy. I think Discourse on Telegram would be a super awesome thing.