Originally posted by Rebel*:

weird, I can find it with a google and its a thunderstore mod but when I open it Thunderstore says it doesn't exist. Even though it says it was updated 2 days ago. https://thunderstore.io/package/ebkr/r2modman/

Your link works for me. Download manually and install.
Add all the mods you want directly from R2modman. Tweak all config files to your likes and start the game locally for a few minutes so the new config files can be generated.
Then upload config files and plugins to the server and share your code with friends.
The code can be found somewhere in settings, not sure exactly where (im not at my PC right now).
Your friends then need to install R2modman and create a profile using your code.