AFAIK keepassXC is the c++ rewrite and runs on Linux, Mac and even windows

the broken earth triology anybody?

How can google track you when you use a dumb phone? Do mean by means of other tech or are you implying they have access to cellular towers?

According to Wikipedia:

Data stored on OneDrive is subject to monitoring through technologies like PhotoDNA.[81] Any content that is in violation of Microsoft’s Code of Conduct is subject to removal

do you already know which hardware + OS combination you are going for?