Some PB803 boards have unused peripherals (e.g., an extra serial port, a second camera, or an SD card slot). Custom firmware builds can activate these features.
Rarely. The MT5510 lacks open-source GPU blobs (Mali-400 MP2). However, some Russian developers have posted LineageOS 14.1 (Android 7.1) builds for mt5510s boards on 4PDA. Search for "MT5510 LineageOS 14.1 PB803." Tp.mt5510s.pb803 Firmware
The most common symptom is the TV turning on (LED blue) and immediately switching back to standby (LED red), often blinking a specific number of times. This usually indicates: Some PB803 boards have unused peripherals (e
MT5510_Android_scatter.txt
preloader_mt5510.bin
lk.bin
boot.img
recovery.img
system.img
cache.img
userdata.img
tee1.img