For android email we got this https://prism-break.org/en/
For your online communication i can higly recommend Riot(https://about.riot.im/) It can do text, voice, video, groups, conference, filesharing. And its fully encrypted end to end. Its build on the distribute protocol MATRIX. And provides bridges to just about anything. -Including our known fediverse platforms Mastodon, Pleroma and others. It does support Telegram too.
The fediverse platforms can be browsed with an app. The best one is Fedilab which is multi platform for Pleroma, Peertube, mastodon, Friendica. Then you got Tusky and subway Tooter.
For backup i cannot recommend Nextcloud enough.
It is THE best backup & cloud solution in the world. You can sign up at a provider or set up your own server. It can backup just about anything from your device, images, files, contacts, sms, calendar… And it has many extentions, one of them also provides access to the fediverse.