Televisions don't need to use high voltages any more
Yes, DC-DC conversion is used in many things, good example is a camera flash - the flash discharge tube needs a few hundred volts
and the usual technique is a power oscillator driving a step-up transformer, and the transformer secondary is rectified to charge
a capacitor. Have a google around for camera flash driver circuits - there will be lots of examples I suspect.
For lower voltages DC-DC conversion often uses a boost or buck or boost-buck switch-mode circuit - avoiding needing a transformer,
but requiring a inductor.
And any convenient switching device can be used for driving these circuits, either bipolar or MOSFET. (In the very old
days the oscillator might be electromechanical even!).