If you run a repair shop, SigmaKey is the gold standard. It costs ~$200 for the dongle but supports:

Here are the most effective and trusted tools currently available. We have evaluated them based on success rate, ease of use, and platform compatibility.

Even when used legitimately, Unisoc IMEI repair is not trivial. Common pitfalls include:

Originally a MediaTek tool, modified versions exist for Unisoc. It requires BROM (Boot ROM) mode access.

Dial *#06# on the phone. Your original IMEI numbers should appear. Insert SIM cards. Network signal should return within 30 seconds.