From what I've seen very little. I _think_ it's something to do with the kind of people who work on embedded systems generally wanting the freedom that comes with making things from scratch resulting in not that much interest in repurposing old things outside of making them work with their overall IoT network.

I recently reverse engineered an e-waste STEM toy from scratch ( https://github.com/padraigfl/awesome-arcade-coder ) and the general response I got from places were:

a. to salvage the microcontroller and other relevant parts (probably worth $4 off a board that would cost $100+ to replicate)

b. a weirdly hostile attitude about the ethics of reverse engineering regardless of the motives (guessing people have been burned a lot with people stealing their designs)

I've mostly worked on the frontend and don't have much knowledge of embedded systems at all but it wasn't anywhere near as hard as I expected. Keen to find some other ESP32 devices to tweak (suggestions welcome!). I guess even if making them unflashable becomes the norm it won't be too hard to just swap the ESP32 off the board with a new one.

The ESP32 (and other ESP chips) are somewhat common in smart home/IoT gear, particularly for devices that are dependent on a cloud service to function. There's a growing trend in the smart home community of re-flashing cloud-dependent ESP32 based hardware with ESPHome, which makes the device fully local controlled, eliminating the risk of the cloud service being discontinued/enshitified.

It's not a particularly common thing yet, but smart home enthusiasts are becoming increasingly concerned about the expense and effort required to replace cloud-dependent hardware because the manufacturer decided the cloud service isn't worth maintaining anymore.

Quite a bit in IoT market, especially in the low-mid tier and Chinese imports. There’s an entire ecosystem of custom OS’s for home automation that runs on these ESPs, ESPHome for example. I have flashed quite a few smart sockets to run Matt/kafka messaging client rather than unknown vendors software that has an open socket to offshore ips.