I've got it. SSH works, networking works, bwfm is up, my system-disk is the sd card so I don't need usb drives sticking out. I love openbsd! Here's the method I used, for documentation's sake:
2 flash drives (1 for sets, 1 for miniroot), 1 sd card (install disk) Download `Raspberry Pi Imager` (https://www.raspberrypi.com/software/) Select Raspberry Pi 4 -> Misc utility images -> Bootloader -> USB Boot Flash to sd card. Flash miniroot78.img -> 1st usb drive Format 2nd usb drive to FAT, download sets, and copy to root (or OpenBSD/7.8/ as the installer expects) Boot sd card (display output optional) When it's done, make sure all drives and ethernet are plugged in Reboot Install openbsd as usual (Make note of sd/mmc device and usb device with filesets) Essentially, it's the reddit guide with fewer steps. I'd have preferred some way to get the EEPROM image without a gui tool, but it works, so I won't complain. Thank you all again for your help! Best, William Long

