The interpretant is essentially the already-baked-in observer here. Whence interpretation? My prediction is you will say that we cannot go any further than this semiotic ground and thus just a brute fact. — schopenhauer1
That's a good point. And it is the point of the semiotic view to generalise or universalise the notion of the observer.
So in the panpsychic view, this is done by spreadiing mind about everywhere, over every scale of being. But who knows what this "mind" is? It is a concept without causal structure or useful meaning.
In the pansemiotic view, it is interpretance or the sign relation that is spread around every scale of being. And so observation is modelled in terms of an ontic process.
Of course that is just a broad brush sketch. Then you have to cash it out in more useful ways. Which is what modern thermodynamic/information theoretic descriptions of the Universe have been doing.
This infodynamic perspective for instance adds formal and final cause - the story of the top-down constraints - to the bare science. The development of structured being is granted an entropic shape, direction and purpose. The universe becomes "mindful" in this self-organising regard. The universe can be considered a dissipative structure that is dissipating hot quantum uncertainty so as to produce a cool realm of robust classicality.
So the panpsychist starts with a reified notion of "mind" and simply imagines diluting it - thinning out its substance until it is there in fundamental particles in some deaf, dumb and blind fashion. The basic question of "what is observation" is simply brushed under the carpet by fading it away to nothing except the regular physics of mechanical masses and forces.
Pansemiotics is part of the new information revolution where observerhood is defined at the Planck grain in terms of "the questions that could even be asked" of a physical locale. Quantum uncertainty is due to the fact of hitting a physical limit where you can no longer ask all the questions you need to to precisify the state of a locale. So the breakdown of observation is exactly determined. Hence the beginnings of (classically certain) observation is also made physically measurable and theoretically tractable.
Once you can say where things stop and start in terms of concrete existence, you are away. And that is what physics can now do.
Every physical constraint is a sign. It is information to be read as a constraint on free dynamics. And information theory can account for both the negentropy of constraints and the entropy of degrees of freedom.
That view of things is now being take back into mind science to account for the kinds of things that brains do in terms of forward modelling or Bayseian information uncertainty reduction.
Consciousness becomes not the generalised substance of panpsychism but instead a massive ensemble of accessible modelling states - a massive ensemble of particulars. In any moment, the brain could be in any number of states that represent a meaningful observer~observables modelling relation. The fact that just one state is selected, the rest suppressed, is what gives brain consciousness its exceptional adaptive variety.
So in pansemiotics, the observer is the interpretance, which is the habits, which is the constraints, which is the negentropy. That is how you go from the highly complex specificity of observing brains to the most simple, universal and fundamental level of observation that is the basic entropic condition of the Universe described through dissipative structure theory.