Modern MOND theories modify the gravitational force at their simplest, they do not presuppose a quantum origin of that force. Ergo they're not creating new fields. More exotic MOND theories (like emergent gravity, mentioned above) reframe gravity as an entropic, not fundamental, force, akin to the "force" that "pushes" heat from hotter areas to colder areas. Again, not a quantum origin. It's still possible emergent gravity requires some kind of quantum component.

Again, the "evidence" we have for "dark matter" is just inserting dark matter post-hoc to explain some mysterious misalignment between theory and data. That's all it is. Mechanisms for explaining that discrepancy are called "dark matter" because people aren't imaginative enough to entertain any other possibilities besides "it's definitely another particle, bro". I'm not saying MOND is more correct, we can't say that at this time, what I am saying is the confidence and zealotry of dark matter advocates is severely misplaced and amateurs do not have a grasp on what exactly is being claimed to notice that there's nothing actually being explained, no theory per se whatsoever, when words like "dark matter" are bandied about, and so feign the confidence that the dark matter die-hards themselves project.

As for Einstein: https://en.m.wikipedia.org/wiki/Cosmological_constant

"Dark Matter" is a name for the observations of the discrepancy. It's not a theory in and of itself. Lots of the theories trying to explain the observed discrepancy (dark matter) include that in their name (like the λCDM theory), others (like MOND) don't. They're all trying to explain the same observations though, so they're all theories of "dark matter".

I don't think it's helpful to lump in MOND under the "dark matter" umbrella, and no one else aside from you seems to do that. It's specifically not about matter nor energy (i.e., QFT) in every formulation that's out there.

Further, MOND does try to explain the discrepancy with articulated theories, just in ways that don't conform to the assumed supremacy of QFT-based explanations.

Scientific theories are usually advanced by finding and then explaining misaligments between existing theories and data...that's how physics works. Scientific theories can often predict future, yet unmeasured data that would not fit other competing theories. This is exactly what occurred with the measure of anisotropies in the CMB. Dark matter models correctly predicted the form of anisotropies in the CMB. MOND theories did not.

Additionally, while the various dark matter theories have the problem of being self consistent and consistent with current observations, but extremely difficult to experimentally confirmed, MOND theories have the issues of not being self consistent and/or not being consistent with current observations.

And yes, the newer MOND theories add additional fields to account for CMD anisotropies:

https://phys.org/news/2021-10-mond-theory-account-cosmic-mic...

"The new model begins by using the original MOND idea of two types of fields that behave together as a type of gravitational force—one is scalar, the other vector-based. Next, the researchers added parameters that suggested gravity-modifying fields generated in the early universe—ones that mimicked dark matter. These fields, they further suggest, evolved over time until they became the type of force described by the original MOND model."

And no, Einstein did not discuss dark energy. A cosmological constant is the most well accepted explanation of dark energy. And Einstein did not add the cosmological constant to his equations because of any cosmological observations, merely his own assumptions as to the structure of the universe.

"Dark matter" didn't predict anything. Dark matter is always and every time an exercise in begging the question. Show me a single dark matter theory from first principles, that doesn't start with assuming the conclusion, and you will show me a dark matter "theory" worth considering.

Yes, that's the general idea of individual dark matter theories. We have an enormously successful cosmological model, lambda CDM, that includes cold, weakly interacting matter. Many theories have been put forth to explain what the additional matter actually is. A few of them are actually not created originally to account for the matter in lambda CDM, such as axioms. But yes, there correct, it's the lambda CDM model making successful predictions, the individually dark matter theories are just along for the ride.

Anyway, you are free to spend as much or as little time as you like considering different speculative theories by whatever metric you see fit. I find it odd that you are a proponent of MOND theories but seem to dislike theories that modify existing frameworks and are continually refined to match observational data.

Au contraire, I am seeking precisely theories that actually modify existing frameworks without merely begging the question. The approach of "oh, must just be more matter but it's weird that we can't see it" is going to be seen as ether or geocentrism is now. It's just grossly unimaginative and ironically doesn't actually modify existing modes of thinking, i.e., assumes that gravity is still a fundamental force if only we could describe it as a quantum field.

MOND is a change to the existing framework that makes predictions from the basis of a theory that actually explains the data "discrepancies" we're seeing vs typical assumptions. The discrepancies are testable with MOND. It's not merely a post-hoc justification of some detailed maps of where matter "isn't". While with dark matter all one can try to do is detect particles that we are already blindly assuming are there. Dark matter enthusiasts love to espouse the "shoulders of giants" thing with their tiny incremental modification to LCDM but they're taking an approach that fails to learn from the historical blunders of physicists before who wanted to assume some substance exists and then try to back-prove its existence with increasingly elaborate and specialized theories of origin.