Hi!
I have experience with ESP32 microcontrollers, and OTA, although not specifically using AWS FreeRTOS's OTA. I am AWS certified, and have looked over the relevant documentation on how they do signed OTA upgrades, and I don't think it should be a problem.
I'm willing to negotiate my price if, after discussing your needs, I'm convinced that there's a significant amount of work needed, but as it's a fairly straightforward process, at this point I don't expect it to need more than 1-3 hours...
I'd be happy to discuss your needs (and, if relevant adjust my bid) in chat - at the very least, you'll get some free advice.
I'm fine working on Windows (I've done a lot of ESP32 flashing off windows)
I look forward to working with you!
Issac