It's a moot point, as Signal isn't going to support self-hosted notification servers any more than it'll support self-hosted communication servers.
Signal works without GMS or any alternative, at the cost of more phone wakeups. This is much more preferable to everyone whose WiFi or data service you use see you connect to "push.myownname.com", or for you to rely in some rando gatekeeping your message delivery.
Signal works without GMS or any alternative, at the cost of more phone wakeups. This is much more preferable to everyone whose WiFi or data service you use see you connect to "push.myownname.com", or for you to rely in some rando gatekeeping your message delivery.