Search for "Huawei B535-232 unlocked firmware" or "B535-232 band unlock BIN" on forums. Look for user Vlik1 or lelik007 (known patchers).
Stock Huawei firmware hides advanced features behind a user agent check. Custom firmware patches the html files within the router’s filesystem to enable: huawei b535-232 custom firmware
: A popular GitHub repository used to unpack, modify, and repack Huawei firmware partitions. Search for "Huawei B535-232 unlocked firmware" or "B535-232