While "universal" versions exist, the most stable global versions for the B315s-607 are typically: Global/Universal Firmware (21.321.03.00.00): Often used to de-brand routers. Search for 21.321.03.00.00 WebUI (17.100.09.00.03):
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When running universal firmware, the device continues to support its core hardware features: Huawei B315 4G LTE WiFi Modem