Sorry, my English is very poor, so I did’t express things that I want to explain clearly in the title.
I see this Topic said, if you turn on Desktop PWAs feature, you can:
So I turned it on,
But when I visit Discourse site, there isn’t have “Install to desktop” option.
The strange thing is when I visit another website which support PWA, there has “Install to desktop”, and I can install it successfully.
And another the strange thing is, I can’t install the later in my Android device, but the former can.