The Nordic Thingy:53™ prototyping platform includes firmware source code, documentation, hardware schematics, and layout files.
For Android and iOS:
The hardware files can be downloaded from the Nordic Thingy:53 product page.
The zip file and its subdirectories contain the hardware design files for the Nordic Thingy:53. The hardware files for the circuit board are available in the following folder in the hardware files zip package:
\Thingy53 - Hardware files x_x_x\PCA20053-Thingy53 Board x_x_x