Which Linux distro should I put on my Raspberry Pi server?

Just about any of them would do. It's like saying "I want to drive from Chicago to Minneapolis in a car. Which brand of car should I drive?" Just about all the car brands will get you there. ;)

At the end of the day, I recommend figuring out your preferred distro if you haven't already and going from there. Most major distributions like Ubuntu, openSuSE, and Fedora have Raspberry Pi versions.

If you're asking for optimizations, you'll find them in keeping as few processes running as possible, and you may get better speeds by hardware means such as purchasing a micro SD card with faster read-write capability or getting a cooling fan for the CPU.

Hope that helps, and props to making and running your own website from home! :)

What people are saying here is generally correct overall. If you are using the rpi as a server, the distro ever so barely matters. You probably wouldn't want a gui (why give away half the CPU and a sizable chunk of memory to something you aren't even going to look at?) and every distro out there has exactly the same server packages available.

I would install the minimal Raspbian and then add the server applications you want. Also, don't forget you can completely shut off the HDMI for a tiny bit of power savings. If you are going to use https, every little bit counts.

The only reason I actually name a distro when normally I'm hugely agnostic, is because Raspbian is the official distro for Raspberry Pi, and therefor can always be expected to support rpi's various idiosyncrasies.

Slackware. The thinking man's distribution. Trim it down ultralight purpose built, or keep it ready to go at a moment's notice. I've got Raspbian on mine, but once I get the 8 gig version, I think I may just pull the trigger on Slacking it up.

Then again, I may be completely insane, because I'm humming and hawing around building a Single System Image out of a pair of them and actually making something roughly analogous to a laptop to go along with it.

To be frank, you probably shouldn't take my advice. I'm clearly a glutton for punishment, and it may lead you to the darker corners of computing related insanity.

Tip - if you are going to run the server 24/7 best to use an external USB=>sata HDD instead of a flash card. Did the flash route and after a while (multiple resets) the card just died, flash does not go well for unexpected power cycling. Best to use a mechanical drive better resiliency and recovery.

I used Raspbian (*versions wernt important), mainly I'd choose a distro that works for the versions of server software that you want to keep updated (i.e. older=Ubuntu, newer=Linux Mint)

I would recommend Raspian Lite and install the server packages that you like. You can secure it similar to any other distro. I think there are checklists online that tell you how to configure it securely (root/sudo/user, ssh, permissions to change on specific folders or files).

I've put Arch and Raspbian on a Pi. I know Raspbian is The Official Raspberry Pi distro, but gee whiz, Arch felt a lot more solid. I ended up using Raspbian to build a 4-node Kubernetes cluster, you just can't do it with Arch.

I'm using ubuntu server 20.04 along with micro-k8s to have a 3 node cluster for kubernetes at home.