I have an issue where I'm trying to load the driver for a LM75 temperature sensor using dtoverlay. It never loads, nothing in the dmesg log. I can load the driver via modprobe and everything is working, but it's my intent to have all drivers set up via config.txt. Posting on the Raspberry forums an engineer with Raspberry figured out what caused it, either missing udev rules, or a change to the i2c-sensor overlay. I figured it would be quicker to add the udev rules to the build (I'm already building a new image using this repo), but I'm not entirely sure how to go about adding the rules. Here's a link to the proposed solution:
https://forums.raspberrypi.com/viewtopic.php?p=2084444&sid=0f6ff6c008b21a7cb50be59a0c813125#p2084444