Your post is not putting forward any argument about Plausability or Probability [...]

Maybe not with enough emphasis, but I did - the other two options of the trilemma seem much more plausible.

[...] you are just saying that the theory is not falsifiable / we will never fins out, like argument about God.

This depends. If your believe includes, say, god reacts to prayers, then we can most certainly test this experimentally. But overall the two may be somewhat similar - unless god or the creator of the simulations shows up and does some really good magic tricks, it might be hard to tell one way or another.

The argument about probability goes something like this: there is only one real universe, where an advanced species like us would evolve.

You do not know that there is only one universe. You do not know that we qualify as an advanced species with respect to cosmological standards.

Eventually we would create multiple simulations.

Will we? What if we go extinct before we reach that capability? What if we decided that it is unethical to simulate universes? What if this is not feasible resource-wise?

If advanced specicies evolves in a simulation [...]

Will they? Can they? I think it is a pretty fair assumption that simulations in general require more resources than the real system or provide limited fidelity. If you want to simulate the mixing of milk in a cup of coffee, you will either need a computer much larger than the cup of coffee or on a smaller computer the simulation will take much longer than the real process or you have to use some crude fluid dynamics simulation that gives you an acceptable macroscopic approximation but ignores all the details like positions and momenta of all the atoms. Therefore I would say that any simulation can at best simulate only a small fraction of the universe the simulation is running in and it is not obvious that a small part would be enough to produce simulated humans.

[...] they create their own simulation.

Everything from above applies, there are reasons why this might not happen. And with every level you go down the issues repeat - can and will they create simulations? And the simulated universes are probably shrinking all the time as well as you go deeper.

Therefore there is only one real universe, but many simulations, so chances are we are in a simulation.

Sure, if there are many simulations and only one real universe, then it might be likely that we are in a simulation. Even then there are some caveats like for example each simulation also has to be reasonably big and contain billions of humans or they can have fewer humans but then there must be more of the simulations, otherwise it might still be more likely that we are not in any of the simulations.

Anyway, this all only applies if there is such a set of nested simulations, then we are probably simulated, but the real question is how likely is the existence of this nested simulations? Is it even possible?

It also could explain why we are alone in the universe.

We do not know that we are alone. And even if we are alone, there are more reasonable explanations then a simulation. And who even says that we would be alone in a simulation?

Holographic theory suggest that the whole universe coupd be a hologram around a 4D black hole or something, so also appears to hint in this direction

It does not. The holographic principle just suggest that for certain theories in n dimensions there is a mathematically equivalent theory with only n-1 dimensions. The best known example is the AdS/CFT correspondence which shows that certain theories of quantum gravity based on string theory have a mathematically equivalent formulation as conformal field theories on the boundary of the space. Whether this is a mathematical curiosity or whether this has some deep reasons is everyone's guess.