I'm not saying you personally have to build a mobile app. I am saying, in the grand scheme of things, if this is genuinely something that matters to a bunch of people, any one of them can build a mobile app and solve your problem.
There are tons of people on HN that hate Electron. If this is actually a real problem, then someone will eventually solve it, and it'll be fine. On the other hand, if a large, sizable community of native developers with tons of experience on the platforms they want 1st-class solutions for don't ever get around to solving it... then it's probably not a real problem.
What was the drive to use 1, self-host and non-federate an instance of Matrix over another platform, and 2, why? With family especially, I would assume a simple WhatsApp/Signal group would have been easier for adoption.
This is how the internet is supposed to be.