Just provide your original site logo (possibly simplified to best suit a favicon), optionally your main colors and your app name also, and this online tool will automatically generate the text to include in the head section and the package of all image sizes, including your site manifest, to upload to your root folder.
In less than 5 minutes in total you have your site favicon in all versions, free, no install and no registration = all what we like here. Kudos!
You can also inspect any URL regarding its favicon choices; very useful for comparison purposes
Free, No registration, No Download/Install required