For various definitions of "secure/stable".
For me, anything which Google can reach and amass information from, and thus NSA, is not secure. Rust on Linux where I am playing with, is fine.
And its not only the "conspiracy style" "why would Google put backdoors in its 'Play Services'", no its more like
"oh Google receives and sends notifications for every Signal message sent and recieved, among other information, such as Device ID, phone number, android version" - in short who is using signal and when.
Signal is amassing huge amounts of information for benefit of Google. Look at their github page, where they even say they want more to amass more data and to "annoy the hell out of users" to make them update - shove updates down their throat a la Microsoft style.