MySQL 8.0

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WITH _k AS (
    SELECT 1 AS n
    UNION ALL
    SELECT 2 AS n
), _points AS (
  SELECT user_id, CASE WHEN n = 1 THEN start_at ELSE end_at END AS date_point, n
    FROM company_changes
   CROSS JOIN _k
   UNION
  SELECT user_id, CASE WHEN n = 1 THEN start_at ELSE end_at END AS date_point, n
    FROM enablement_changes
   CROSS JOIN _k
), _drank AS (
  SELECT p.user_id, p.date_point, DENSE_RANK() OVER(PARTITION BY p.user_id ORDER BY p.date_point) AS dr
    FROM _points AS p
   GROUP BY p.user_id, p.date_point
)
SELECT d1.user_id, d1.date_point AS start_at, d2.date_point AS end_at, c.company_id, MAX(s.status) AS status -- or MIN if status disabled is stronger then enabled in the same time
  FROM _drank AS d1
  JOIN _drank AS d2 ON d1.dr = d2.dr-1 AND d1.user_id = d2.user_id
  LEFT JOIN company_changes AS c    ON d1.user_id = c.user_id AND d1.date_point < c.end_at AND c.start_at < d2.date_point 
  LEFT JOIN enablement_changes AS s ON d1.user_id = s.user_id AND d1.date_point < s.end_at AND s.start_at < d2.date_point 
 GROUP BY d1.user_id, d1.date_point, d2.date_point, c.company_id
 ORDER BY 1,2,3;

user_id	start_at	end_at	company_id	status
189	2020-12-12	2020-12-20	88	disabled
189	2020-12-20	2021-02-10	88	enabled
189	2021-02-10	2021-03-02	88	disabled
189	2021-03-02	2021-10-15	169	disabled
189	2021-10-15	2050-01-01	169	enabled