One of my personal projects for many years, restartOS, has seen some good active development lately, mostly for ARM based systems (think Raspberry Pi, Orange Pi, etc). The premise of it is that I take a Debian-based Linux distribution and I finess it so that it runs completely in memory. It is very similar to the way a live-boot ISO works, but with some key differences. The most important is that it’s not a pre-installation environment. It is a full OS intended to be used for whatever creative purposes you can find for it. Because it does allow for you to flag some files as being persistent, you can customize it as, say, a file server, and mount external storage as read/write and then every time your system reboots it will start up your file server for you. This is one of many use-cases. It can run containers (using Podman), which opens the door to running any number of services on it. But at the end of the day, the OS itself is non-persistent, meaning any changes made while it is running are lost on reboot. This makes the OS more secure, since it is much harder for a virus to get installed on it. It also makes the OS more reliable, since a reboot resets the OS back to the same configuration that it had when it first booted. It also makes it fast. There are packages that can be installed (like the UI, Chromium (Chrome’s open source counterpart), Podman, GlusterFS, Filezilla, etc.). The base OS is less than 300MB! Podman add less than 20MB to the base. Just with those 2 packages, you get a container server that can boot from a microSD card and since there are no regular writes to the card, it can last for decades.

https://www.restartos.com