In the latest version of Illustrator (25.2.1) If you try place a linked vector file through Libraries into a document that is in a different format eg. CMYK into an RGB document or RGB into a CMYK Document and it is a vector, GPU acceleration is disabled. This does not occur in Illustrator 24.

I've tested this by opening a CMYK Document, placing a linked CMYK file and everything works as expected. If you place a linked RGB vector it will cause the GPU to stop working. The opposite works the same way, placed a linked CMYK file into an RGB document and the GPU stops working. The only work around is to "Place a copy" of the libraries image.