Linked transparency ignored in document color mode CMYK
I've noticed that, at least as of Illustrator version 30.1, transparency in linked files is ignored while the document color mode is CMYK and the View Preview mode is GPU. It does not seem to matter if the original is in CMYK mode or not.
To reproduce the issue, create two Illustrator documents. In the first, draw a few objects on the artboard, setting the transparency for a few of them to anything noticeably different, and save it as Test1.ai. On the second document, set the document color mode to RGB, set the View Preview mode to GPU, and place a linked file of Test1.ai. It should look normal, as designed. Now, change the document color mode to CMYK and notice how any transparency becomes ignored. However, the second document will export or print the design correctly. You just cannot Preview it correctly using the GPU.
I tried to post the Illustrator files to test with. But, UserVoice crashes whenever I try it.