The Preview feature in Sparkle works well. But I wanted the ability to allow access to the preview from outside of my network. That would be handy for collaborating with a client or in my immediate case, allow my daughter access to my development work. So I decided to write up how I handled it for anyone that needs this feature.
You will need to install ngrok via a terminal session on your Mac. You can find ngrok here - https://ngrok.com/ and you can signup for free.
With ngrok installed all I had to do was preview the site in the Sparkle app and get the port that Sparkle is using for the preview. Then I opened a terminal session and typed the command ./ngrok http 14444 which installed the VPN tunnel on the same port (port 14444) that the Sparkle Preview is using. Your website is now visible from the internet until you kill ngrok, shut down the terminal session or shut down Sparkle’s preview. When you run ngrok it gives you a URL that looks something like this http://e1c32a8b.ngrok.iothat you can then share with your client.
The neat thing is that since you are pointing to the preview port your changes are instantly available from the internet. So you get collaboration with your client in real time.
PM me if anyone has questions.