Surge suppressors are typically MOVs.

Utility lines carry many surge opportunities with them. As you can imagine, the substation and typically the overhead distribution circuits are all outside. They are susceptible to lightning strikes and very commonly nearby lightening events. They also suffer phase to phase arc over events which cause the protector to open. Those protectors have a re-trip feature which will reconnect the line after an arc over occurs. Distribution circuits are also switched to another source and voltage adjustments are done by a switching event. Lots of opportunity. These surge events present a high voltage, high frequency but low energy signal on the utility circuit. Well, all except direct lightening strikes.

An MOV shunts when the potential difference exceeds it's voltage rating. An MOV is only a small component wired between the two input power lines. It can and will shunt (short) any voltage presented above the rating. However, it can only handle a very small amount of energy. This makes it a good device to mitigate the effects of utility surges, again except lightening strikes.

Surge suppressors typically have many MOVs to increase the amount of energy they can shunt. These are sized based on the electrical storm frequency and severity of the area. MOVs do not last forever so the type with failure indicators is nice to have. A single surge suppressor cannot be effective protection against near or direct lightning strikes. I typically specify one at the service entrance, another at each distribution panel and the final MOV contained within the equipment PSU . If there is not one in the PSU, that device gets a small surge suppressor. The result is three MOV devices in series to protect each critical load.

Almost all electronics have an MOV in their circuit. I took apart a Bitmain PSU and looked but I didn't find one. There are two thermisters for start up surge protection but I didn't find MOVs.

If they did have an MOV in the circuit I would say no you don't need one unless your genset is exposed to potential direct or nearby lightening strikes. Obviously, you need one because the PSU is not equipped just to cover the mile away lightening surges. If you want to protect against nearby strikes, you'll need 3 surge suppressors. This would be good to do if you are in an area prone to frequent electrical storm activity. You can study the "let-through" voltage and energy specifications to see how to properly size each suppressor.

Can you just put in whatever you found... LOL no. That will not protect your system from lightening induced surges.