I apologise for disappearing for a few days. Dealing with stress, in particular due to this discussion, and with more ‘professional’ stuff. I have not read everything in the thread that got posted since I last replied here yet, and will probably not be able to do so quite right now.

I think the misstep that you’re taking is equating ‘material’ with ‘physical’ or relating to ‘(physical) matter’

But then what you mean by ‘material’ also encompasses non-material things, which doesn’t align with how the word ‘material’ is used in philosophy. This also supports the thoughts that I have been left with for a while at this point that there is no conflict between Marxism and idealism. Just between Marxism and some forms of idealism that are often presented to encompass all of idealist schools of thought.

Also, can you provide a source for your definition of the word ‘material’? Also, as of right now, I do not understand what exactly it is that you mean by it if not that a ‘material’ object is one that consists of matter (and, perhaps, that a ‘material’ process is one that involves material objects, etc.).

I could be wrong: are you referring to any particular Marxists as a source for your definition of materialism and it’s coincidence with idealism?

I never claimed that materialism ‘coincides’ with idealism. What I have claimed is that Marxism doesn’t conflict with idealism (in particular, with the views that I subscribe to).
Strictly speaking, my claim is incorrect, because at least usually Marxists do seem to take as an axiom that all ideas depend on matter in some way, but

1. I don’t see any significant conclusions that are drawn from that assumption that conflict with idealism.
2. Judging by how often Marxists who criticise/reject idealism don’t actually mean idealism in general, but just some idealist schools of thought. More specifically, ones that only distinguish mental stuff out of non-material. These would be people like, for example, (some of) idealist mathematical intuitionists seem to believe (as opposed to materialist mathematical intuitionists).

Personally, I haven’t come across a single Marxist who treats materialism and idealism as compatible

I do not treat them as compatible, except in the sense that there are types of materialism of different strictness. I don’t think that anybody here subscribes to strict materialism that posits that nothing but matter exists, for example.
What I am saying is that Marxism is fundamentally ‘agnostic’ in this sense. All of the relevant conclusions can be made in various idealist and materialist frameworks, especially if we allow for some basic rewording. Again, at the very least currently I am not aware of any relevant conflicts.

Although, I think that all the ‘idealism vs materialism’ arguments do lack an evaluation of a view that neither matter nor ideas have any sort of ‘primacy’ in any reasonable sense, considering that idealism and materialism are often defined through specifically the ‘primacy’ thing (as opposed to through what is labelled as ‘existing’, which is how the relevant terms are defined in at least some traditions), and, bizarrely, I have not encountered the position that I just outlined yet.

idealism does not equate to ideas simpliciter

Not sure what you are trying to say here.

1. If you mean that, literally, that words ‘idealism’ and ‘ideas’ are not synonymous, then that is obviously correct.
2. If you mean that idealist schools of thought do not generally say that ideas are the only thing that exists, then yes, that is correct. In particular, I do say that matter exists.
3. If you mean that idealism does not necessarily claim that ideas have primacy over matter, then there is an issue. While, for example, I claim that there are ideas (such as what mathematicians study) that are independent of matter but not vice versa, and that I also claim that there are ideas (like, for example, our imagination and perception of things, including what is studied by mathematicians as well as how that stone that you just threw skimmed over the water) that either have dependency on matter but not vice versa or, at least, that matter has some sort of ‘primacy’ over those, I do claim that some ideas do have some sort of ‘primacy’ over matter. If you do not define ‘idealism’ and ‘materialism’ through some sort of ‘primacy’ or even existence of relevant objects, then how do you define those?

In any case, my main point is that, so far, I do not see any significant conflicts between Marxism and idealism.