GLSL syntax higlighting is broken

GLSL been broken for very long time (always?). However in 16.0 it become worse.

Here is default highlighter, as example:

Structure is gone now. Keyword/Builtins we broken in previous releases.

Before in 15.0 it was solvable by using third-party language server, but now it no longer available: adding new "Generic stdio language server" doesn't affect opened files. And newly added server disappears, from the settings, after IDE restart