Signal and DeltaChat, as well as Simplex and some others e2e communication solutions, are adequate from a technical point of view.
The main issue is always adoption. You can have the most convenient way to safely communicate with people, it'll be useless if nobody you're talking to wants to use it.
So, since Signal is very easy to set up and use as well as the most adopted, it's currently the best pick for regular conversations.
Selfhosted services like Nextcloud/Immich aren't nearly as dependent on a critical user mass like Discord/Matrix, but the principle is the same.
If you host for family or friends, they may even use it if you convince them to switch. But when the setup, which doesn't consist of redundant instances and isn't maintained by a small army of SysAdmins 24/7, inevitably breaks for longer than a few minutes, most will switch back to the easy, reliable option.