ANTLR Grammer file repository
ANTLR v4 Grammer file (.g4) links
Public repository
There are many files including VB6, VBA, Python, Ruby, PHP, T-SQL, JSON, Kotlin, Java Script, HTML, CSS and so on.
https://github.com/antlr/grammars-v4
Visual Basic (.NET)
Microsoft Official
https://ljw1004.github.io/vbspec/vb.g4?raw=true
The link above is on here.
https://docs.microsoft.com/ja-jp/dotnet/visual-basic/reference/language-specification/