Years ago I posted about how I was sharing selected contacts between Google accounts.
The solution I discussed at that time has gone paid only so I went looking for alternatives.
I found CoContacts that works great for me.
CoContacts has a free offering that supports 3 users with 3 shared groups with 100 shared contacts that sync daily. If you need more than that you should be paying for it.
I'm using it on G Suite accounts but it will also work with regular Gmail accounts.
It works so elegantly that I couldn't remember what I was using for contact syncing!