Had a similar problem with hybrid unit -107 db signal, on the off chance I wondered if trying the other side of the house just to test the EE signal would work but not expecting to be able to connect to SM2 30 ft away., Anyway to my pleasant surprise the hybrid unit connected via one of the BT wifi mesh disks in same room - signal strength now -91 db and no need to buy external antennae. It seems you do not need an ethernet connection or to be very close to the SM2 for the connection to work, just a strong wifi signal.
I just got the Hybrid Connect (Halo3+). My connection was two bars (96dMb+), good but not excellent. I purchased a couple of SMA antennas on Amazon: “Andven 4G LTE Antenna, SMA Male 10dBi Omni-directional External Antenna for 4G Router Trail Camera Mini PCIE Card - Black (2 Pack)”. I also pointed the device at the closest cell mast (using cellmapper dot net to find it), and played around with antenna position - went with both straight up. I’m now getting 91 dMb or less. Right now (which I assume is a low congestion time - Saturday morning) I’m getting 86 dMb. The icing on the cake, the status colour code has changed from green/good to blue/excellent in the BT app ✅