I can recommend creating this favicon ICO from the command line. Mac instructions:
Install ImageMagick with the following command (install Homebrew if you don't have it)
brew install imagemagick
Save a 32x32 favicon PNG image from Affinity Photo or whatever
In your terminal navigate to the folder where the PNG image is
Run the following command to convert the PNG to an ICO
magick convert favicon.png -background transparent favicon.ico
More information: https://www.imagemagick.org/script/convert.php
