Is fractional PLL the key functionality that defines whether a microcontroller is able to generate an analog TV signal?
Of course not. You always have the option of running the MCU's main clock at the required frequency (or a multiple thereof) so that everything else can be derived by simple counters.
The MCU datasheet will show you the external clock input along with the range of frequencies that you may apply to it. Pick a frequency within that range for your external crystal or oscillator that meets the needs of your application.
For example, a frequency of 14.31818 MHz (4 × the 3.579545 MHz color subcarrier) might be a good choice for generating NTSC video.
MCUs that do serial communication over UARTs frequently run at frequencies like 11.0592 MHz, which is a multiple (6×) of 16 × 115200 Hz that happens to be less than 12 MHz, the upper limit of a common MCU back in the day. If your MCU can do 20 MHz, you might choose 18.432 MHz (10×) instead.