Stage History(Opportunity) Related List is visible in Classic only.
The related Stage History list is already added to all Opportunity page layouts but it is visible only in Classic.
How to enable Stage History(Opportunity) Related List to be visible in Lightning Experience?
Stage History are available in both classic and lightning if they are added to the page layout.
In your case, it is not coming to Lightning. The possible reason is:-
There are two component available in Lightning app builder that can show related list on a lightning page. They are:-
Realted list will show all the related list available on the page together where as Related list single allows to select single related list and show it alone.
You might be using Related list single component. You can add one more related list single component with showing stage history.
