Hi,
You can change the manifest-overrides.webmanifest (it is a JSON file) inside app\theme\web and provide extra settings to overpass the icon=maskable any error. I have been using this one as a example and it does not raises any error according to pwabuilder.com. When you deploys it goes to app\deployment\web
{
"name": "TravelRequest",
"background_color": "#aaa",
"icons": [
{
"purpose": "any",
"sizes": "192x192",
"src": "/icon-192.png?638309727850015776",
"type": "image/png"
},
{
"purpose": "any",
"sizes": "512x512",
"src": "/icon-512.png?638309727850015776",
"type": "image/png"
}
],
"dir": "ltr",
"start_url": "/",
"short_name": "TravelRequest",
"lang": "en-US",
"display": "standalone",
"theme_color": "#000000",
"description": "Travel Request App"
}
Hope this helps!