In my experience Belarusbank and Paritetbank ATMs are commission free.
Payments in state agencies are ONLY online using a local online bank. Banks are not always nearby!
Use platform.gov.by for the online registration. It's fun and English version bugs. If your address has an extra building section, e.g. Building 13-1 (and 1 makes a separate building not entrance!) the platform might cut out the "1".
My full package for real estate deal guiding includes:
spotting an apartment / house,
interacting with the sellers,
assistance in setting up a bank account,
linguistic assistance with the deal's paperwork,
assistance after the deal (TRP application and interaction with utility services if necessary).