I have tried it both with https://fonts... and simply as //fonts... config.toml. It seems to work in both cases.
I have tried your fonts in my CSS style sheet and they work. Please see attached image from a test blog to confirm that these are the fonts you seek.
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Might I suggest that you use double quotes in your CSS file for the font names because that is how I have it in my custom_style.css, e.g., font-family: "Itim", cursive;
I have been away from Hugo and my work on my website for some time now and am aware that many changes have happened in the interim. My version of Hugo is v0.37 in case that helps.
Cheers!