julia_setup() fails

I'm in the process of moving stuff to a new computer, but can't get JuliaCall to work there. So this issues came from a clean slate (not so clean anymore) where i had just installed the newest versions of Julia (via JuliaUp), R, RStudio, Renv, and then among many other R-Packages also JuliaCall.
I get issues from within a renv controlled R project (using JuliaCall version 0.17.6) but also when just opening a plain r session, just installing and loading JuliaCall and running julia_setup(). Specifying force=TRUE and rebuild=TRUE doesn't help.
First I tried with the original Julia install by JuliaUp, then I let JuliaCall install Julia itself, and when that failed too I installed Julia in a manually specified location without spaces in the path. JuliaCall now always uses that last install (and i dont know how to get rid of them as i cannot find an uninstaller and windows only knows of one, but thats a problem for another day).
I get this error message:

But I don't always get the warnings.

I tried running this in a fresh julia repl (not launched via JuliaCall, but separately) (and first accidentally used the juliaup install for that) where it complained about Suppressor and RCall missing. So i installed those. There was another eror after that which i didn't record, but is probably the same as im reporting a few lines down. I then realized that my julia repl is using a differen julia install then JuliaCall does, so I tried the same from a REPL of the newest julia install. There might have been some other tries like changing julia environment and trying to install suppressor and RCall via JuliaCall (which I assume didnt have any effect because julia_setup doesnt work). But in the end the spot where i ended up is that if i execute the command which julia_setup complains about in the separate julia REPL then i get this error:

At some point I think it also complained about something from JuliaCall missing when i ran that line in the Julia REPL. It stopped complaining about that when I installed JuliaCall in the plain (non-renv controlled) R environment.
Sometimes through all this I might also have gotten other error messages. It seemed quite inconsistent.

Overall I feel like at this point I'm just aimlessly trying out things and am lost and directionless. I need a more principled approach to find a solution. I hope someone here has an idea how to approach this problem.

Start by reproducing the failure at the julia_setup() entry point in both a plain R session and the renv-controlled project, recording the complete error output rather than relying on the screenshots. Compare the Julia installation and environment used by JuliaCall with the separate Julia REPL, including whether Suppressor, RCall, and JuliaCall are available. Done means the setup completes consistently or the specific installation or environment conflict is isolated.