One problem with really old web browsers is that they don't support *ANY* of the modern web standards. Virtual servers are extraordinarily common, but old browsers don't support it. (I'm not talking "a server running in ESX," I'm talking where "one host acts as multiple domain names"
You can get around it by setting up a web proxy that "translates" new websites in to something readable to an old web browser. This would require running the proxy on a machine in your local network, and you would point your Mac Plus at *THAT* machine, which would present an interface to let you choose which website you want to go to.
Web Rendering Proxy is probably the best of them, but it renders the pages as a picture to the old system - there are other ones that "translate" new style web requests to old, with various successfulness.
Web Rendering Proxy: Use vintage, historical, legacy browsers on modern web - tenox7/wrp
github.com