In short: A PRNG(Pseudo-random-number-generator) uses a seed based on some input. Usually the current date, time, number of CPU cycles etc. If you were to plug in these exact numbers again, the seed would always be the same, resulting in the exact “random” number output.
True RNG however would not depend on that. A true RNG would always spit out numbers that are not predictable, no matter the circumstances. Unfortunately this is not really possible. Even with the input you mentioned, static noise, transistor distortion it would still be a PRNG. Luckily these inputs are almost impossible to recreate, so one could it call “true randomness”.
So yeah, you can hack Slot machines if you were to find out what inputs the RNG in the machine uses. But depending on the input, it can be quite hard 