The lsp (language server protocol) features where introduced in one big (incomplete) pr.
The idea was to first have a remote server component which is available from the openHAB installation a user has connected to the vscode extension.
Later there also should be a local language server component, to increase speed and ressource usage.
Both controibutors (vscode extension side and the main contributor for the initial work in openhab core for the server part) are no active contributors anymore.
I (as probably last leftover regularly contributor to the extension) have tried to get into that lsp stuff different times but have decided to no longer put any effort in it.
The only thing I could do easily, is remove the whole lsp part.
But this would also cause many complains. Therefore I am not doing anything, before doing wrong anyway. (#Lindner , sorry for the german joke. I couldn’t resist. 
)