I have been using a DS18B20 on GPIO08 of a D1Mini for a long time now. The rest of the board was full so I didn’t have much choice. This worked fine under the old way but now with the One_Wire methog, the system kicks the configuration out claiming that GPIO08 is part of the flash interface.
I know on certain sensors you can allow_other_uses: true but this doesn’t work on the One_Wire system.
GPIO8 is used for onboard flash memory, it’s forbidden to be used as anything (ok, not “literally” forbidden, but you are asking for trouble doing that):
Honestly, i don’t understand why these pins are even available on some boards …