I have several LibreOffice documents of very big size, currently around 2300 pages. And I create a PDF with LibreOffice after every update I do.

With Ubuntu 23.04 this 2300 page doc spent 1 minute to load. You can't change anything until it loads.

With Ubuntu 24.04 this 2300 page doc spent 12 minutes to load. I uninstalled LibreOffice that came installed by default and installed the LibreOffice again but now from snap, and time of loading the doc was back again to 1 minute

As I was angry of having to resize some apps using the mouse + keyboard, I decided to try some other flavors of Ubuntu.

I installed Kubuntu. I opened the doc of 2300 pages and time of opening is now: 10 seconds

I see also that in Ubuntu the system was eating 5,9 GB of RAM just to run. In KDE is 1,6 GB only.

So if you want speed I recommend Kubuntu flavor.