Thoughts on how a Death Note version of Disco Elysium works:
Firstly. The ugly tie is capable of perceiving and talking to Ryuk. They get into an argument with each other filled with profanity and yelling during their first conversation. This happens early enough in the game that it's likely the player hasn't fulfilled enough conditions to be able to notice Ryuk, leaving them with their tie incoherently yelling at nothing.
Harry: "Kim, my tie is having an argument with a person that isn't there."
Kim: Kim pauses, his reaction betraying nothing but a slight exhaustion. "Fascinating, detective."
(If you have this encounter while able to see Ryuk but unable to hear the tie, the conversation is equally confusing.)
Second. Everyone has some surface level awareness of the folklore of shinigami, but it's varied and contradictory bordering on useless in most cases. Only the truly powerful or truly strange have interesting or useful information. Evrart suspects that Wild Pines employs them for union busting which is why him and his brother have the identity fuckery going on. The Paledriver vividly remembers making love to one back before electrical power was invented. Passing an Inland Empire check with Joyce will earn a summary of how the corporate class has treated the shinigami like a hostile SCP and have spent billions in R&D trying to figure out how to kill them. Cunoesse was given a Death Note a couple years ago but wasn't literate enough to use it, so now she has the empty book binding of a Death Note and a few paper shivs (touching the book binding or getting stabbed by Cunoesse are valid ways to gain the ability to see shinigami).
Third. Dodging the effect of the Death Note can be done in multiple ways. Evrart uses Harry's name too much for Light to not pick it up through the rumor mill, but the right drama checks can make Light doubt whether Harry's true name is actually Tequila Sunset or Raphael Ambrosious Costeau. Alternatively, either of those names can be internalized in the thought cabinet to make his legal name invalid. Regardless of how it's done, what's more important is right afterwards when you need to make a multiple dialogue checks (primarily drama) to convince Light that Kim went to the same lengths and it's not even worth trying to target him. Ryuk will contribute to this bluff if you've convinced him that supporting your efforts will be much more entertaining than letting Light win.
The Pale would absolutely factor in to the supernatural elements, but I'm not entirely sure how. Pale Aged Vodka might be a temporary power up to both see shinigami and be untargetable by the Death Note. I think Ryuk would be scared of the Pale, at the very least, even if he can't give any insight into what the fuck goes on in there.