Customizing Do-It-Yourself Landing Pages for SEO

I have a bunch of domains going to the same landing page I have created with relevant content.

My question is, how much do you have to change on the page for each domain so that google will see it as a different site?

I changed the title of the page, and I plan to add some custom keyword script so that each domain name is placed in there too at the start

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SEO UK|Search Engine Marketing