After I posted this I vaguely remembered a Stereophile review with measurements, so I have the data I was looking for. The Brilliance Control plays a huge role in what the amp sees. I’m currently running the Brilliance Control at ~1:00 position, which according to the Stereophile article should put minimum impedance somewhere between 2 and 4 Ohms, which should be fine for most good amps.
https://www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-measurements