I too have a 2021.5 Berk 34B. I found the fresh water drain. I am starting the process of winterizing and overcoming the learning curve. Step one is drain the fresh, and flush and drain the gray and black tanks. Done.
Next I found three low point drains. Two in the water bay, hot and cold, and one in the compartment in the bedroom where the hot water shut off and bypass valves are. The heater is bypassed and hot/cold lines to heater are closed. Before that I shut off power to the aqua heater.
Now I drain the aqua. Simple step.
Now running the water pump to purge that?
Am I ready to put in antifreeze? My concern is not getting it into the fresh water tank. There is a T valve where the fresh water tank is. Ithink I flip it closed. When closed to the tank, it is open to a drain.
Now my biggest concern is the shower miser. When I use the water pump to suck in antifreeze, how does this work with the shower miser so antifreeze doesn't end up in the fresh water tank. I wish Forest River had a plumbing schematic.