Link several domain names to a white-label site

Hello dear mates,

I have a white-label website and several domain names.

The provider (for example Shopify) allow to link 1 domain only.

Therefore, does exist a way to link all my domain names to my website in order to optimise the SEO ?

For now, I simply redirect them to my website but it is useless for the SEO.

So, how would you proceed ?

Thank you.