@yannick_beot - Thanks for highlighting that /Users/{{id}} doesn’t support filtering.
I tried below using a filter but still wasnt able to get it working
https://{{master}}:12105/identityiq/scim/v2/Users?filter=userName eq "1605124" and urn:ietf:params:scim:schemas:sailpoint:1.0:User:entitlements[application eq "IBM DB2 Database Server"]&attributes=userName,urn:ietf:params:scim:schemas:sailpoint:1.0:User:accounts,urn:ietf:params:scim:schemas:sailpoint:1.0:User:entitlements