When using sildurs vibrant shaders, all entities (Mobs, dropped items and xp) are completely black, including the arm/item I am holding.

Tested with multiple different versions of sildurs shaders. High and medium, older and newer versions.

Gonna test older versions of immersive portals.

Restart the game and try again and see whether entities are black. The shader compatibility is very hacky and sometimes problems get fixed by restarting the game.

Ok I can reproduce this issue now. You can use sildurs shader 1.22 which does not have this problem.

I'm using 1.22, and restarted. Still black

Already tried using sildurs 1.22 (medium), and restarting.
Nothing works.

what's your optifine version? And show the log

Possibly fixed.

Fixing this also leads to the fix of chocapic shader compatibility and beyond belief shader compatibility

I will release the new version possibly tomorrow

fixed in 0.26