“publishing them on the App Store” was intended as (perhaps imprecise for you) shorthand for all of these distribution issues.
You very much can develop Safari extensions on Windows or Linux because they use largely the same APIs as Chrome extensions as I already mentioned. Any differences are well documented. The only thing you need a Mac for is, again, distribution. If not for that it’s really not that different to developing a website that will open on Safari without access to an Apple device.
Once upon a time Apple had a separate Safari extensions website where they allowed extension developers to publish or sign extensions after registering for free as they recognised these barriers. They could either be distributed on Apple’s extensions gallery or you could distribute the files yourself.
You very much can develop Safari extensions on Windows or Linux because they use largely the same APIs as Chrome extensions as I already mentioned. Any differences are well documented. The only thing you need a Mac for is, again, distribution. If not for that it’s really not that different to developing a website that will open on Safari without access to an Apple device.
Once upon a time Apple had a separate Safari extensions website where they allowed extension developers to publish or sign extensions after registering for free as they recognised these barriers. They could either be distributed on Apple’s extensions gallery or you could distribute the files yourself.