Neat project. A few years ago I tried and failed to get a junkyard Toyota security ECU from a ‘96 4Runner to work for remote lock/unlock in my ‘94 Land Cruiser with an eBay key fob. I might revisit it with this approach - cheap and easy RF analysis software/hardware would have eliminated a lot of guess work … though if memory serves I think the real headache was decoding wire colors in the security harness, which were not all explicitly labeled in the manual for “security” reasons.

What approach are you going to take to try and determine the cryptographic key of your device? Is there some way to hack and “root” your gate opener controller?