Jellyfin is the sever bro. You can implement your own client and choose from a pretty decent variety of clients on Android and most platforms. Only Android TV really suffers from required first party support, but the api is documented and we encourage you to make your own or port it to whatever front end you’d like.
I will literally never use signal until they change it so data is archivable in some form and syncable across devices. I won’t recommend people use it. I don’t care how secure it is. Security is important, but usability is where telegram has signal beat by miles. I’m not hiding nation state secrets. I’m horny posting and chatting with other weirdos that like to be animals on the internet.
I think you misunderstand the purpose of open source. This is something someone made for the community out of the goodness of their heart and a desire to create. You can build on top of it or use it as a base and completely remake it if you want, but they’re not making money off this… So your attitude towards them and what they’re offering to everyone for free is honestly quite rude and entitled.