Great question — answering as the UphillTech team:
The last I checked, FreeBSD installed its EFI boot loader using the fallback filename ( EFI/BOOT/bootx64.efi on the ESP). rEFInd should locate that and offer to launch it as the "fallback boot loader." If you don't see it, perhaps you skipped a step during installation or selected an incorrect option; or maybe bypassing the option to create a new ESP confused the FreeBSD installer and caused the boot loader to not be installed. I'm not an expert on FreeBSD installation, though, so I'm afraid I can't be more specific.
Full answer by Rod Smith: https://superuser.stackexchange.com/a/1217372 (CC BY-SA 3.0).
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