For thos who are still looking for the solution below is the solution.
After some trying around I solved it by using the following SQL qeuery:
UPDATE sales_order as SFO
INNER JOIN customer_entity as C
ON C.email = SFO.customer_email
SET SFO.customer_ID = C.entity_id
WHERE SFO.customer_is_guest = 0
I have exactly the same problem (just migrate from m1 to last magento 2.4.3 version )
All my configurable product are at the end of the list and I'm customer of many Amasty extension who interact in that case :
Amasty Shopby but ALSO AMASTY advanced Sorting ...
Configurable are at the end and doens't respect the position
Waiting their support for answer , ...