RocketMod should only be acquired from the patched version included with the game's base installation. Using older versions (i.e., versions from archives / third-party websites) won't work, especially for Linux hosters.
There are still plugins there.
There are, which is why I didn't make a comment about plugins.
My prior understanding was that Hykscraft offers pre-compiled versions of a lot of the plugins linked on the official RocketMod subreddit, and provides (will provide?) services to future plugin developers.
I don't have anything to say regarding that, so I didn't. :X
devtrackers.gg