How to submit A/B test variants to Google Analytics?

Question

Google Analytics

Maybe someone came across. We want to test different versions of the main page of the site. A/B test setup will be carried out by developers, without using Google Optimize, etc.

The question is, how to transfer the A / B test variant to GA? I read that it is possible through user parameters, but I did not quite understand how exactly, maybe someone will tell you. GTM is not installed.