Is the RT84 the same hardware as the RT3S?
There appear to be some similarities in the look and feel.
RT84 - Not compatible
Re: RT84
No.
Only works with RT-3S aka MD TYT-UV380
TYT aka Retevis make loads of radios which use the same case and display etc, but are completely different when you open them and look at the hardware
Same applies to the new Baofeng DM-1801, which looks idential to last year's DM-1801, including the firmware which looks identical, but they completely replaced all the internal hardware with different CPU and DMR chips, hence the new DM-1801 is no longer compatible.