Is the SUNSYNK-SG05LP3-EU-SM2 SUNSYNK-20K-SG05LP3-EU-SM2 compatible with the Sunsynk CHNT DTSU666 (3ph + CTs)?

Yes — listed by the manufacturer.

The manufacturer's published pairing data lists these together.

Manufacturer's compatibility listListed together in the manufacturer's published pairing data. A cited document reference is being added as datasheets are processed.

Pairing details

Both products

Design a system with this pair