You will just have to wait until Lemmy officially supports push notifications. It is planned. Anything else is a hack involving polling.
Boost sends me notifications on replies
That's what I am using but I don't get the notification unless I open the app
Might be your settings or permissions
does Voyager work with ntfy?
Maybe not what you want, but my solution is email notifications with InstAddr
I've kind of been using that way more than disposable email at this point. The app notifications always work and get received immediately.
I am not sure how trustworthy it is though. I've been using it for years, even for school and work, which is probably not the wisest, but it's worked for me better than others.
Which app does that?
I get them on sync
I've come to.like.this behaviour. No notification overload.
But you do receive notifications from other apps like reddit,Facebook and X. So why is is that you are okay with Lemmy case of no notification?
I don't use those apps.
I have notifications for some other apps that do require prompt action, like WhatsApp.
Thunder has experimental support for it. You'll also need a unifiedpush distributor installed. F-Droid has a good explainer on UnifiedPush at https://f-droid.org/2022/12/18/unifiedpush.html
Replies, mentions and messages, afaik. Not sure what other kind of notifications you'd be expecting.