LTR Classic not compatible with OS Ventura 13.7.8, which cannot be updated on iMac 27" (2017)

On my iMac 27" (2017) it's not possible to update the OS anymore. Therefore, the LTR Classic catalogue, which was recently updated by a brand new MacBook, cannot be opened.

The question:

is there a way to update the iMac OS at least to Mac OS 14?

I know there's a possibility to downgrade the LTR Classic to a previous version, but I've recently done so much work  with my new Macbook which would be lost if I did it.

Any suggestion?

Titusminor