With the current available latest Release of Pwnagotchi, v1.5.3, it’s not possible to use the UART (TC / RX) GPIOs on a Raspberry PI. Thats because of the wrong compiled Waveshare V2 Display Driver.

You have to recompile it as root with a different header file.

cd /usr/local/src/gratis/
make rpi-remove PANEL_VERSION=V231_G2
make rpi-clean PANEL_VERSION=V231_G2
make rpi PANEL_VERSION=V231_G2 EPD_IO=epd_io_free_uart.h
make rpi-install PANEL_VERSION=V231_G2 EPD_IO=epd_io_free_uart.h

After installing the new driver, reboot and your UART Pins should be available again.