The link you gave includes this link to a tutorial on how to install on Android:
I just tested with Firefox 92.1.1, and it works as described:
I do not use Chrome, so I cannot test that, but:
If a user dismisses the banner, will it appear again? No. Not unless the user clears their history. We want to make sure users have a good experience. We will likely be changing all the heuristics over time.
Source: Add to homescreen banner on Android - #2 by DeanMarkTaylor - Announcements - Discourse Meta