Roblox Luau Language Server based on Lua by sumneko.
Make sure you don't have both Lua by sumneko and Roblox LSP enabled.
https://marketplace.visualstudio.com/items?itemName=Nightrains.robloxlsp
https://devforum.roblox.com/t/roblox-lsp-full-intellisense-for-roblox-and-luau/717745
Roblox OS Community Discord Server: https://discord.gg/c4nPcZHwFU
You can download the extension with precompiled binaries here: https://github.com/NightrainsRbx/RobloxLsp/releases
If you need to build your own binaries, follow the instructions at https://github.com/sumneko/lua-language-server