DeGoogled phones don't have Firebase push. Makes life a little rough, but do what you gotta do.

Telegram and Signal get notifications regardless. Amethyst now has Unified push capabilities. You can host Unified Push on your own Nextcloud.

Nextcloud Services app on Andrpid can poll your server every 5 seconds or so. This seems to be the only way to get your self-hosted Nextcloud Talk to get notificatipns.