That article in Signal is bogus. It is entirely based on speculation from how funding comes in, and also either ignores, or misunderstands how Signal fundamentally works.
The EFF recommends Signal, and it’s one of the most secure ways to communicate.
https://ssd.eff.org/module/how-to-use-signal
You can make your own decisions, but if you just grab any random arguments, you’ll find a reason to doubt everything.
I’ve been running a pair of cyberpower systems for over a decade. I had to replace the battery in each of them once, but they’ve been working great.
I assume newer ones use some sort of Li-Ion battery tech, but mine are just plain old Lead Acid.