You might be interested in Tiny Core Linux [0], then, especially piCore. After the initial read from the persistent media,
everything is in RAM, the entire filesystem. You are working exclusively in memory until and unless you run a specific command to save everything you care to save back to that media again.
I have it running on a Raspberry Pi so that my already sparingly-used SD card's lifespan gets extended to, hopefully, several years. I have never seen the green writing LED light blink on without me specifically triggering it.
I primarily use it as a cronslave [1]. It has ~50 separate cronjobs on it by now, all wheedling away at various things I want to make happen for free on a clock. But if you live out of a terminal and could spend your days happily inside tmux + vim or emacs -nw, there's nothing stopping you from just doing this. Feels a lot like driving stick shift.
[0]: http://tinycorelinux.net/
[1]: https://hiandrewquinn.github.io/til-site/posts/consider-the-...