Is the EcoFlow EF-HD-P3-S1 EF HD-P3-29K9-S1 compatible with the EcoFlow Integrated (RS485 + CAN)?

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

CT specification
cts: Integrated metering (RS485 + CAN to BMS) · note: PowerOcean inverters have integrated metering. External meter not required. Wi-Fi, Bluetooth, WAN, and 4G connectivity built in. · type: Integrated · cableLength: N/A · maxExtension: N/A

Both products

Design a system with this pair