If you want to switch servers to Linux I’d highly recommend Arch Linux because it’s lightweight and very snappy, with next to nothing unnecessary installed by default - you add the stuff you want. Ubuntu is a performance dog.
Having said all this, if you’re not familiar with Linux, setting up a headless PC with network shares and mounting local drives etc. is not something a *nix newbie would likely consider simple as it’s all terminal based and it’s going to feel very foreign. There are good guides on the net though, and happy to answer questions if you decide to go that route. There’s an Arch installation guide on this forum also: