Single registration on different sites?

Question

WordPress

Hello! In general, the essence of the question is as follows:
1 There are 2 sites on different domains
2 Both on Wordpress + 2 also cost Woocommerce
3 I want to make a single registration for these sites, if registered on 1, then you can safely go to 2
I found that You can do it through SSO.
Can anyone have experience and tell me where to dig?

Answer 1

- Merge database into one - bad
or
- Merge cookie into one - bad
or
- Intermediate gateway for authorization and setting cookies. As done on habr projects for example.