[selcuka]

I don't think that would work as many people also use Cloudflare etc.

You may try using BuiltWith which is a paid service:

https://trends.builtwith.com/websitelist/Shopify

[ttt3ts]

It works fine. Just issue a HEAD request when you are unsure and rotate proxies a lot l. Takes a bit of infra but definitely possible.

[selcuka]

I mean simply querying nameservers won't work.