Is length matching is necessary on I2C, UART signals, and SPI?
No, these signaling types don't need length matching. Operating at 1.2kbps-115.2kbps (UART), 100kbps-1.5Mbps (I2C), or up to about 50Mbps (SPI) over the usual board-level or cabled (UART) distances, the signal wavelength is still much longer than the electrical medium size. The signal quality will not be predominantly influenced by the electrical length of the conductor, but by parameters such as parasitic capacitance and the strength of pull-up resistors. A general rule of thumb is if the signal wavelength is less than 10x or 20x the size of the electrical medium, transmission lines are required and it is a "high speed design."

Additionally, none of the interfaces use differential signaling, if UART is RS-232. There are serial standards like RS-422 and RS-485 that use differential (balanced) signaling.