Happy to assist!
That is correct, due to the 3G sunset by the end of 2022 panels will need to be upgraded to 4G LTE. Alarm.com is supporting 3G until the end of 2022 but you may notice signalling issues before that, as local infrastructure is reallocated.
2GIG Go!control panels use 345MHz sensors, these can be re-used with the Qolsys IQ Panel 2+ with 345MHz radio QS9201-5208-840.
That panel would let you re-use Z-Wave devices and 345MHz sensors. If you have the 2GIG TS1 or Image Sensors, those could not be re-used.
You can purcahse the panel via the previous linke, this comes with a complimentary month of service (Surety Home) as well. This would result in a new Alarm.com account.
A programming guide for the Qolsys IQ Panel 2 w/ 345MHz radio can be found here: