1. Did you enable the "Improved add to homescreen" flag in about:flags? Either way, can you flip the value and try again? It would be helpful to know if this changes things
2. Does this phone have google play store installed?

1. No I didn't, and doing so results in no improvement.

Note that, to try again, I used chrome's menu option, since it no longer prompted to install automatically, which it did the first time (before logging this bug). It showed a dialog saying it was adding it, but still nothing actually appears on the home screen.

2. No, I don't think so. Looking in the Apps settings, I see 'Google Play services', but that's the only Google reference. It uses a Huawei store, iinm...called 'HiApp'?

One thing I've noticed is that this phone runs 'EMUI':

http://emui.huawei.com/

My money's on that being the source of the problem. Still, I think the 'add to homescreen' feature of PWAs needs to also work on phones with modified UIs such as this.

Can we see if this is reproducible for us?

Given that there's no play store, I would expect "Improved add to homescreen" would fail and fall back to old homescreen shortcuts and I'm guessing that that flow is broken on this device. I suspect this isn't webapks at all

I tried on Huawei P9 (doesn't have Play Store). At first it did not add a shortcut after 'Add to homescreen' from menu. I see that the App needs permission to do so.
And it worked as expected on Allowing to add shortcuts.

I enabled it here, Android Settings -> Applications -> Chrome -> App permissions -> Set individual permissions -> Create homescreen shortcuts -> Set to 'Allow'. 

And just to be more clear, it doesn't go through the WebApk install flow as expected. It just adds the shortcut/WebApp based on the website.

I can concur that adding the permissions to allow chrome to add to homescreen (different to those described for p9 though) allows it to work as expected - though I'm not sure about the 'webapk install flow'.
I did have to manually add it though, but I guess that is because I've (attempted to) add it on previous occasions.
I also noticed that, once I ran it from the homescreen, it then popped up the prompt to add it again...and when I accepted, it displayed a message (I think) saying that it was already added.

I am wondering, then, if this is a permission chrome should be asking for when *it* is installed?

Thanks to both of you - that clears things up!

So it sounds like a specific OEM modification that Huawei has made to android which we can potentially add some logic to account for. It requires some investigation though into if there's programmatic control of this setting. It's not a default android permission but maybe huawei added their own.

The re-prompting is also a bug :/

Finally, the "webapk" thing I was referring to is when we add a small android app and a shortcut to that rather than just a shortcut to chrome. Unfortunately that depends on the store on the device so isn't feasible to fix (but would probably be acceptable if we fix the first part)

Interesting - sounds like the Android INSTALL_SHORTCUT permission isn't granted by default on the Huawei device. Perhaps we should see if we can handle that case more gracefully.

Specifically, we check if there is a launcher broadcast receiver / ShortcutManager support (https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/ShortcutHelper.java?type=cs&q=isAddToHomeIntentSupported&l=411). Seems like we should also check if we have INSTALL_SHORTCUT permission too.

Friendly ping. Is there any update on this issue.

As there is no action on this issue for long time closing this issue. Request you to update your Chrome to latest #66.0.3359.158 and verify. Feel free to file a new issue if the issue is still reproduced at your end.

Thanks!