I'm not sure this is possible from the docs, but can you remote debug an vagrant ASP.NET webforms site using omnisharp remote debugger? I can't find much info on this anywhere
EDIT: Trying to setup omnisharp for VScode https://github.com/OmniSharp/omnisharp-vscode/wiki/Attaching-to-remote-processes
I'm using this vagrant setup https://github.com/dmitry-zaets/vagrantfile-windows-iis-mssql/blob/master/Vagrantfile
I also added ASP.Net to this box
DISM /online /enable-feature /featurename:IIS-ISAPIFilter
DISM /online /enable-feature /featurename:IIS-ISAPIExtensions
DISM /online /enable-feature /featurename:IIS-NetFxExtensibility
DISM /online /enable-feature /featurename:IIS-ASPNET