I use an "Edimax EW-7811Un" (aka the N150-nano) usb wifi adapter. Only costs 8 USD on Amazon.

It uses the urtwn driver in OpenBSD and FreeBSD. It works...ok. Super small and a handy built in blue-LED so you know when it's powered and connected. I tend to leave it plugged in even when I reboot into macOS because it's pretty much ignored there due to lack of out of box macOS kernel module I believe.