Release: CNMSPP99000-7.6-Unified Infrastructure Mgmt-Server Pack-- On Prem
Using the "Quick Search" in USM does not search the other IP address information.
"Other IPs" is populated from the CM_COMPUTER_SYSTEM_ATTR’s attached to the system (key=OtherIpAddresses), not directly populated in the CM_COMPUTER_SYSTEM entry. The quick search (non-advanced text search in the top-right) only searches CM_COMPUTER_SYSTEM fields of name, ip, caption, description, dedicated, os_type, os_name, os_version, os_description, origin, mac, user_tag_1, and user_tag_2.
Using the Advanced Search (top-right Actions button->Advanced Search) will allow you to then select an "Advanced..." field and one of those should be OtherIpAddresses.