Hello @ThomasWilliamson welcome to the /e/ forum.
Unfortunately the /e/ recoveries do not seem to work for this device! I have one! (Mentioned briefly in this issue Error message after clean Q install (#2840) · Issues · e / Backlog · GitLab)
Only Heimdall will communicate with the device in Download mode.
Fortunately TWRP works fine for this device and is found here Samsung Galaxy A3 2016 (Exynos).
Your first boot into TWRP can be tricky, please check the paragragh so named here.