I think at the moment Lighthouse uses 144px minimum requirement, which is the first requirement Chrome checks. I believe this implementation comes from here:
https://developers.google.com/web/fundamentals/engage-and-retain/app-install-banners/

To summarize Dominick's thoughts from https://codereview.chromium.org/2773353002/

Lighthouse should check that the Web Manifest provides icons which are at least 48x48 device independant pixels in size for all supported Android densities. Since the largest screen density on Android is xxxhdpi Lighthouse should check that the Web Manifest provides an at least 192x192px icon.

Assigning to Sam to his thoughts on what we should do

Assigning to Owen since Sam is OOO

Owen: Ping!

Assigning to awesome Sam for awesome insight

More details from dominickn@ from the bug:

I'm aware of this push, and I fully support it. However, it is a reality of
native development that you need to support multiple icon sizes to suit multiple
devices. Having a flat pixel-based cutoff is the wrong move going forward,
especially because launcher icons aren't fixed in size across different
densities.

My preferred solution is something like:

 * remove the 144px cutoff
 * use the minimum size passed into InstallableManager to do the manifest level
check (instead of 144)
 * have Lighthouse be able to check the icons for common devices and their
required densities.

Improving WebAPK eligibility predictability should be done through Lighthouse,
and then ensuring that any site that passes Lighthouse will pass the client
check.

I think there's a distinction to be made here between a warning and an error. The consequences of having an icon upscaled are not too large -- I'm sure some people would notice a 144px icon scaled up on a xxxhdpi screen (I'm not one of them), but I don't think it should keep something from being installable.

My preference would be to allow installation with 144px (potentially upscaled to xxxhdpi and even higher DPIs in the future) but tell the developer that there may be some devices where it doesn't look great in Lighthouse. (e.g. "We recommend providing a higher resolution version of your icon. The largest one you provide will have to be upscaled on 10% of devices.") That would avoid changing a requirement we've held for a long time (not that we can't, just that I don't think it's worthwhile here) while still guiding developers to the best experience.

Sam, the original concern is that a given Web Manifest will generate a WebAPK on some devices but not on others depending on the screen density of the device.

How do you suggest we address this? (Or should we ignore the concern?)

I still think that's important -- I think that probably implies that we upscale icons which are too small on very high density devices.

Can we discuss this bug at an upcoming installability weekly meeting? June 21st seems to be the first opportunity looking at your calendar Sam