I would like to add, the main 24V supply has reverse polarity protection with a diode on GND. The only risk I can understand is the internal 24V event passing through GND system & damaging the MCU. I can separate the 3.3V GND traces/pads from rest of the system GND, but it would still have a common point at the 3.3V LDO. So I am wondering, if I can just protect this common point?
I have looked in isolation transformers, but they cannot handle the 1A power requirement for my 3.3V circuit.
Another option is 1:1 DC transformer. that should physically separate the GND for 3.3V circuit. But haven't found a suitable option on LCSC.