I was surprised how exact the measured temperature and humidity is, until I opened the case for a look at the board and the devices on that board.
The sensor is a SHT30, so this is no surprise, I use SHT31 sensors from Sensirion, a Swiss sensor producer, for my sensor network. You can get these sensors mounted on practical boards by Chinese suppliers, or even on a board for Wemos D1 mini (LOLIN).
The processor is a Holtek HT66F0182 8bit microcontroller.
The e-paper display contains the inking WFT0000CF41 on the flex cable. Google knows nothing about it.
The e-papers from Good Display also have WFT... marks on the flex cables; don't know if this means it comes from them, or just the flex cable comes from the same source.
The signals are not easily accessible, I would need an interconnector like gcormier used.
The e-paper seems to be glued from the front side to the case, so I can't see if there is any device on it, but it looks like the glass is slightly extended on one edge.