I am currently completing my bachelor's degree in computer science. Once this is finished, I will begin a master's program. I assume this information is not really helpful to you, sorry.
I am trying to reduce my dependency on phones/android since years and try to use Linux (NixOS) for everything and I would say I've been quite successfully. The only application that is holding me back from abandoning phones entirely at this point is Signal, because it requires a primary device and only the official mobile apps are currently suited for this task. Flare looks promising, and the PR has already been merged, but it is not enabled by default due to other issues. For online banking, my bank supports SmartTAN that requires a scanner, but this allows me to do everything via a browser.
I have to say as someone who uses NixOS I love systemd, because it makes a lot of things very easy. For example hardening services ( systemd-analyze security) or replacing cron (system timer).
Thanks. I already looked at Flare. Even though primary device support has been implemented (https://gitlab.com/schmiddi-on-mobile/flare/-/issues/128), the last time I used it this feature was disabled by default, because the developer strongly advises user not to use it (https://gitlab.com/schmiddi-on-mobile/flare/-/merge_requests/94).