I know there was a (somewhat?) successful package repository and manager called Teapot and Teacup [0] respectively that was run by ActiveState but I don't believe it's actively having packages added to it. I really wish there was some new development along these lines to allow for github repos to be imported (I think I've seen this in Golang). As far as the language server goes, I'm guessing that would be really difficult to implement for Tcl since each command can essentially implement its own DSL.

[0] https://wiki.tcl-lang.org/page/Tcl+Extension+Archive