External DLLs in local development

Hi everyone,

We are assisting a customer who is trying to refer to an external DLL in Durable Function on C#.

Following these public posts, we recommended that they try manually creating a bin folder under home/site/wwwroot
https://www.sharepointpals.com/post/how-to-refer-custom-dll-or-assemblies-in-azure-function/
https://stackoverflow.com/questions/36559509/how-do-i-use-external-assemblies-with-microsoft-azure-function-apps

They want to test this in local development first. What is the equivalent location where they should place the bin folder locally?
They have tried these locations but apparently it isn't working.
(project folder)\bin\Debug\net6.0
(project folder)\bin\Debug\net6.0\bin

Also, am I understanding correctly that they should be able to use #r to refer to the dll after placing it in the correct location? They are running into an error like "#r not allowed in script" in their testing, but it seems to be supported per the public posts above.

I don't see any official documentation about the recommended way to reference external assemblies.