Almost every hobby brain-VR setup in the wild runs ChilloutCharles's BrainFlowsIntoVRChat. It reads any headset BrainFlow supports and sends over forty OSC parameters to a VRChat avatar: focus and relaxation scores, alpha to gamma band power for each side of the head, heart rate and breathing where the hardware reports them, and a machine-learned classifier for thought commands you train yourself.
It went viral when a player called Rantis posted a clip of moving their avatar's ears with a Muse 2. It is MIT-licensed, still actively maintained, and has its own community Discord.