I have a customer using many iPad Minis. 2's and 4's. They're also having failing wireless modules, but it doesn't seem related to the 12.3.1 update.
In fact, I can make the wireless come back on, randomly, by holding the home and power button together for a reset. I have yet to determine how long that lasts. Sometimes the wireless is ‘off’, and has a greyed out switch, sometimes it’s ‘not connected’ but shows no networks, and other times it’s either connected or sees networks to connect to (depending on if I reset the network settings)
The Mini 2’s don’t have this issue. They’re breaking cameras, but no wireless. So it seems limited to the A1538’s.