Stats reports on a per-category basis?

Check out the Data Explorer plugin.

You can use this to generate reports from SQL queries, here’s a query that will capture some of what you want to track.

-- [params]
-- date :start_date = 2020-04-01
-- date :end_date = 2020-04-29

SELECT c.id category_id, COUNT(DISTINCT(t.id)) topics, COUNT(p.id) posts, sum(p.like_count) likes, sum(p.reads) reads
FROM categories c
INNER JOIN topics t ON (t.category_id = c.id)
INNER JOIN posts p ON (p.topic_id = t.id AND p.post_type = 1)
WHERE p.created_at BETWEEN :start_date AND :end_date
GROUP BY c.id
ORDER BY COUNT(p.id) DESC

You can share these reports with groups via the Data Explorer UI:

And it will appear in the group page like this:

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