@JHH you have seen the wide range of tyre pressures. Very few gave any indication of what tyre, what terrain, tubeless or not and so forth. I go with the lowest I can get away with that still gives a smooth ride, without tyre instability when cornering hard. Similar to
@Mikerb, having found a set up that works, I increase pressures if I am going somewhere with pointy rocks, or I need to reduce rolling resistance.
On this point about reduced rolling resistance, it is a myth that higher pressures automatically reduce rolling resistance. It does on tarmac or other smooth surfaces, which is why road bikes always have high pressure (that and the very narrow tyres). But when the trail is covered in roots, or is stony and/or rocky, then the tyre becomes part of your suspension. The tyre absorbs the hit rather than bouncing back off the object. When I first bought an MTB, I used 60psi front and rear and got shook to bits on my hardtail. I bought a full suss and was still being badly shaken. It was o0nly then that I discovered the huge benefit that lower tyre pressures can bring. It was this video that was a revelation.
Tech Tuesday - Find Your Tire Pressure Sweet Spot - Pinkbike
OK it's 12 years old, but it is still pure gold. Read the words, watch the video.