Push notifications self hosted without Apple Dev - Pushover?

I am new to Mattermost. I setup a self hosted instance on my server. I need push notifications to work. I thought I might be able to get Pushover to work but cannot figure it out.

I guess to make it easy, it is possible to do push notifications without needing an apple developer account using another service?

I tried using TPNS but could not get it to work consistently.

Any help would be greatly appreciated. Thanks in advance!