Hi @kouliscon
You need to follow a grouping logic as the below:
1. You need to get the list of distinct users from your List where status = In Progress
So Initialize an array and call it Users Array; in my example it is array of disticnt IDs

In my example the list is called Reservation List , so only retrieve items where status = In Progress by using the ODATA filter Query

2. Now you need to Loop on this Get Items to append the distinct Users ID
Reservation ID is the User in my Example, so first you check if it is not added before then append it to the Array

3. Now you will have to loop on the distinct array of users , Get the related items specific to this users by using the ODATA filter,
So dependent whether you will save email in your array , you can use the odata filter as UserID eq 'Current Item from Array'

4. you can use the output of the GetItems 2 in a create HTML Table and use the output in send email.