Yeah I'm not super happy with Signal's level of openness, but I also wouldn't call it proprietary. It is open source and I could run my own server if I really wanted to, but that would just make it harder.
At the time we were moving from a walled garden to one of 3 encrypted OSS solutions, and I had all of them until we naturally coalesced on one.
SMS at the time didn't work due to not having cell service, and while we "have" RCS now to solve that issue, I don't know anyone who uses it.
Robot vacuums are something non-tech people love, then they use the app and they don't love it anymore haha.
Shout out to Valetudo, which saved the day on our chinese roombas.
I am not quite happy with how the current iteration of the documentation no longer supports DIYing the firmware, it is actually still possible and you don't have to use dustbuilder.