Can you? Yes, it is .NET after all and any .NET language can be used to write .NET apps. VB is supported on .NET 5 as a platform including ASP.NET Core.
Does it have full feature support and templates? No. And based upon what MS has said there are no plans to provide such templates.
However MS has bounced back and forth between VB being fully supported and not. We are back in the "not the future" phase and with .NET 6 MS said they didn't see VB as viable for ASP.NET Core. VB does support .NET 6 as you can partially read here. But the runtime is evolving to support more questionable, performant, newer cases and some of that requires language support. MS has made it clear that C# is the language for that. So you could write an ASP.NET Core app in VB but you might run into some scenarios where VB doesn't have the language constructs needed to properly work with some changes in the framework. I'm not aware of any at this time that are critical. But you'll have to do the legwork to convert the C# project templates to the equivalent VB templates.
As an aside, one "migration" approach is to keep all your code in VB but create the ASP.NET app itself in C#. Since the bulk of your code is likely backend then it remains in VB as normal and just the front end controller/runtime stuff would be sitting in C#. It isn't ideal but would be a bridge.
Another approach might be to migrate your app to .NET Core 3.1. This did support VB if I remember correctly. Once you have the project migrated you can more easily upgrade that project to .NET 6 as the changes are minimal.