Of course it does, but it's limited. GIN does not support range searches (needed for <, <=, >, >=), prefix or wildcard, etc. It also doesn't support index-only

Of course it does, but it's limited. GIN does not support range searches (needed for <, <=, >, >=), prefix or wildcard, etc. It also doesn't support index-only scans, last I checked. You cannot efficiently ORDER BY a nested GIN value. I recommend reading the paper.