@halfbit_ @trexplex Visual Studio Code is a Microsoft-proprietary variant of the "Code - OSS" project, governed by a restrictive EULA which you can read at https://code.visualstudio.com/License/ . Only the proprietary build is permitted to access the Marketplace to download extensions, per the Marketplace's terms of use, which you can read at https://cdn.vsassets.io/v/M190_20210811.1/_content/Microsoft-Visual-Studio-Marketplace-Terms-of-Use.pdf (see points b and f). Further, Microsoft itself makes many partially-proprietary extensions, such as Pylance and OmniSharp, which you are explicitly or implicitly forbidden to use with non-Microsoft builds.
VSCodium is an actually-FOSS variant of "Code - OSS", but, again, almost nobody uses it because of the above barriers Microsoft has put up. Also, language servers aren't "for" VS Code. The protocol started there, but since it's (really) open, many other editors have added support, or have extensions that implement it.