Change user agent edge

I see this has been asked in other Communities and for other OSes...I am using the latest version of Catalina.

In Safari I need to set a specific User Agent of a particular site.

I use this page often and since I am a Mac only user, I need to set the User Agent to a Chrome Windows browser every time I have to use this particular site.

There has to be a way to make a certain user agent automatically active when accessing a particular site.*

How can this be done in Catalina (or Big Sur)?

And if this cannot be done, I would like to understand why, as this seems like something that can very easily be done..and should be available

*The site I am using is a federal government site, so I seriously doubt they are going to update their website due to browser issues.