When I mentioned in my previous post that VueScan does not support the DS-620, it was because I checked all of the currently supported Brother scanner models on the VueScan site beforehand. Contact VueScan and ask them what timeframe you might expect support for the DS-620. If it is beyond March 15th, and Brother cannot provide assurance that they will have their software working by that time, then why wait on a return?
I would recommend that any replacement scanner decision should be preceded by checking the VueScan supported scannners, so you do not have to relive this Brother experience. For any Vuescan supported scanner page, scroll all the way to the bottom of it, and see if it is supported on macOS without any vendor software or drivers. That is critical.