the filter would need to be an exists statement. Again, you would use the API Explorer to discover everything you need for this. Clicking into the Template Users listing you can clearly see the object code and all the fields being kept in this table. The relevant fields would be the template ID, since this is a possible joining point, and the user ID, which is how you are identifying your user. A sample exists statement might look like the below:
EXISTS:a:$$OBJCODE=TMTU
EXISTS:a:templateID=FIELD:ID
EXISTS:a:userID=your four user IDs, all separated with tabs
In plain english, this kind of text translates to:
line 1 -- show me any template team member (i.e. person in the people section of a project template)...
line 2 -- where the template ID on that template team member is equal to the ID field on your template report...
line 3 -- and the users I'm looking for are Debbie, Becka, Ann and Crystal
Please read up on exists statements here:
https://experienceleague.adobe.com/docs/workfront/using/reporting/reports/text-mode/create-complex-text-mode-filters-using-exists-statements.html?lang=en