First and foremost, congratulations on your effort in this great remake! Just one question: though I don't exactly remember how it was done in the original, I can't seem to figure out how to use the Decoder Ring (from the monolith burger) on the encoded message from the astro-chicken arcade. I tried just picking the ring and left-clicking directly on the message (all actions inventory-wise) but it did not work. How can it be done?

You are supposed to do it manually. That's how the original game was! Try it and let us know!

Essentially, what I described above (picking the ring in the inventory and using it on the message) has been done manually. By doing that, no message of an "incompatible" action appeared but nothing happened either. Clicking on the message with the ring, simply resulted in the disappearance of the ring (as being used, indeed) but nothing happening following that (no message appearing decoded, not even after re-reading the message after the use of the ring on it).

No you're misunderstanding, the game never translates the message for you. All it does it show the code to use to translate the message. You have to manually write it down with a pen and paper and figure out the code. The game never has the message appear decoded.

Oh, right! Indeed, I misunderstood... Strangely, I thought that what I was describing was more or less the case in the original game, but there is obviously a false memory there... Ok, thank you both, pretty clear now!