sorry for the delay

i don't know that much about concurrency in general, so take this with a grain of salt

i feel like monitors are potentially an improvement over bare locks, but they tend to perform poorly in manycore settings and are still vulnerable to deadlock, perhaps more so due to their implicit nature. (i see that you point this out with respect to java, and also that it doesn't really have monitors.) fundamentally, blocking synchronization of any kind is incompatible with modularity

you misspelled brinch (rip)

there are lots of versions of actors, and the most influential one effectively didn't have any concurrency at all, so it's important to disambiguate in the text that you're talking about the one in agha's 01985 dissertation, which is also very influential. also your footnote says it's from "1986"; is that a different document by agha with the same title?

objects with their own threads (like concurrent actors or like processes in csp or erlang) are not the same thing as monitors, contrary to your assertion in the 'concurrency in oberon' section. there is a well-known duality between message passing between threads and control passing between monitors, but the mechanisms have quite different ergonomics and common failure modes

it's surprising that in a discussion that surveys original-modula, modula-2, csp, erlang, active oberon, c, c++, concurrent pascal, object pascal, superpascal, joyce, newsqueak, old squeak, alef, limbo, golang, java, and ada, you didn't mention javascript at all. in browsers and node, javascript's concurrency model was originally that of original oberon — each event handler runs to completion in succession — which strongly suggests that the concurrency facilities it has added more recently might be worth a look. those are python-like async/await, sometimes caricatured as 'colored functions', and web workers. also it might be worthwhile to at least mention the π-calculus

my uninformed viewpoint is that js, erlang, haskell with its stm, and (non-async!) rust are the languages with the most promising approaches to the concurrency problem. all four of them work hard to be safe (unlike the entire rest of the js language), though i think their concurrency safety guarantees are all to some degree fragile. except maybe haskell, which i haven't tried

your reference [31] https://www.jtolio.com/2016/03/go-channels-are-bad-and-you-s... doesn't purport to show that no single concurrency construct is adequate, as you claim, or even that communication channels are inadequate; rather, it argues that the implementation in golang of that concept is inadequate, because golang implements them inefficiently, because it can't garbage-collect processes, because there are some design errors, and that because golang also offers other concurrency constructs (as you propose for oberon+), it's hard to avoid concurrency bugs. though certainly not conclusive evidence, this runs strongly against the conclusion you are using it to argue for

also your bibliography incorrectly abbreviates 'per brinch hansen' as 'hansen, p. b.' rather than 'brinch hansen, p.' a few times

i hope this is helpful, and i'm glad to see you're exploring how to solve this problem! feel free to copy or excerpt my comments elsewhere if you think it would be useful