This (or something like it?) has been available for ages, but the only time I've ever actually encountered it in the wild is with links to a JIRA project.
We have this instant app feature in our roadmap for more than 2 years. Every time we start with it, we run into the endless list of difficulties to get it to work. Max size, different modules, shares resources etc. It's hell on earth for most devs. That's why you see almost no apps having it. The idea is nice from a Google perspective. I would rather just add a link to each app in the playstore which goes to the app website. Up to the developer to create a web version of it. But of course this gives zero control to goole
Zillow has been one app I’ve seen using this - visiting their site resulted in an offer to use the app without installation.
A local news site uses it, however as that's in a (distant) second language for me, and I discovered their app doesn't let me select to copy-paste words into a translator, it wasn't useful. Probably just an issue with their app implementation however.
Screenshot -> OCR -> Translate
I have two: CBC News and Yahoo Finance.
(You should be able to find them in the list of apps in Settings)
I think the Weather Channel does / did have an Instant App