I’ve been closely following Motorola’s introduction of new models and it looks like the XT1671 will work on Republic, but I’d want official confirmation from Republic. Based upon the specs at Motorola Moto G5 Dual SIM LTE AM 32GB XT1671 (Motorola Cedric) | Device Database | PDAdb.net , it is for the US market and (based upon T-Mobile - United States - Wireless Frequency Bands and Device Compatibility ) supports all the bands/protocols (and more) that T-Mobile uses. It is now on Ebay for $250.
Personally I like this model (vs. the XT1687) for it’s smaller size, removable battery, and dual SIM. I wish it had dual-band WiFi, but the specs don’t indicate that.
However, I’m not eager to give up my perfectly fine Moto X (1st gen) and the grandfathered $10/month plan, so I’m willing to wait.