I am having the same issue. It seems that add to Home Screen is meant to add a bookmark that opens in the browser, and the button will be replaced by Install if a PWA is detected.
For kbin.social it’s never detected. I can’t hit the install button because it never shows up. Add to Home Screen just opens a new tab in the browser
I did test PWA in general by using apps.Starbucks.com and if I wait a few then the button changes to install and I get the PWA.
So I’m not sure why this is failing for kbin
Is there some way to force the browser to detect a PWA or do a force install, on android?