I was able to get push notifications by installing NextPush on my /e/ OS phone. I have not used it extensively, but it appears to work only for cases when the message originates from the Talk web UI. The Nextcloud Talk application on my phone is not registering with NextPush or the Unified Push Provider running on the Nextcloud instance.
One thing that puzzles me is that I have the F-Droid Nextcloud Talk installed on my /e/ phone using MicroG. I removed NextPush from the phone since this release of Talk does not integrate with NextPush as a distributor. If I post from the Nextcloud Talk Web UI, I get push notifications just fine. If I post from a Nextcloud Talk on an iPad, I don’t get any notifications on my phone. How do posts from Web UI successfully notify?