I'd have to revive ST's package which provides support for ConTeXt syntax and
now trying it with vim/coc, but wonder whether you're using TeXLive or lmtx?

I'm trying with the latter on Debian (Sid)...


I have only tested it with TeXLive. But if lmtx provides a lua interpreter with kpathsea bindings, like the usual texlua, then it will surely work. If that's not the case and you installed lmtx in a nonstandard location, you will need to set an environment variable to specify the location of the interface XML files.

Best,
Augusto