This sucks for developers, but it's also really bad for open source. The only way to get notifications working without arbitrary limits for several open source messaging apps is to run your own notifications server and then you'll need to build your own copy of the Android app for whatever service you're running.
Examples:
1. Rocketchat, which uses this as a sales funnel (I strongly recommend against using it for this reason)
2. Mattermost allows you to use their free notifications server but without any uptime guarantees unless you pay. I haven't used it enough to know if this is a problem in practice.
3. Nextcloud is pretty great, no limitations on using their notification server, but it would be problematic if you require a high degree of privacy and need a fully private setup
4. Dishonorable mention: Odoo who don't even provide source code or a license to build their mobile app yourself
Setting up a notifications server takes some technical work, but nothing too crazy.
But then, you need to get your private app published in the Play Store. Impossible. Brick wall for most people.
Examples:
1. Rocketchat, which uses this as a sales funnel (I strongly recommend against using it for this reason)
2. Mattermost allows you to use their free notifications server but without any uptime guarantees unless you pay. I haven't used it enough to know if this is a problem in practice.
3. Nextcloud is pretty great, no limitations on using their notification server, but it would be problematic if you require a high degree of privacy and need a fully private setup
4. Dishonorable mention: Odoo who don't even provide source code or a license to build their mobile app yourself
Setting up a notifications server takes some technical work, but nothing too crazy.
But then, you need to get your private app published in the Play Store. Impossible. Brick wall for most people.