Is the Sunsynk SunC1-LV01-(Acure) SunC1-5.0LV01 (Acure) 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.