No shuffle for Photos slideshows...how can that still be?

There is a workaround of sorts for that. Try this user offered AppleScript: 13 - Shuffle Photos for an Instant Slideshow in Random Order. It can be found at my tutorial page:  P01 - Applescripts from Photos’ User Tips Compiled as Applications. The script will be downloaded as an application so when you first launch it Control (right) - click on it and select Open from the Contextual menu.

Be sure to tell Apple about the missing feature as Terence suggested.

How can I upload Catalina and still enjoy shuffled slideshows?

I am simply selecting an album in Photos, then select this album in the System Preferences > Desktop and screensaver as the source for the screensaver. Running the screensaver will show a shuffled slideshow.

Or use an apple Script to start a slideshow from a shuffled album, for example:

Script: A Randomly Shuffled Slideshow in Photos with Titles as Notifications

or Script: Shuffle Photos for an Instant Slideshow 2018

It shuffles automatically when you select an album and then run the script. It starts out in full screen and displays the slides randomly. You can download the script compiled as an application so you can put it in the Dock and click on it after selecting an album in your Photos library. You can find them here: P01 - Applescripts from Photos’ User Tips Compiled as Applications

The script is just a work-around. It is shuffling the photos in the album before using the shuffled photos as a slideshow. There is no option to shuffle a slideshow in Photos anywhere. Use the slideshow themes in the System Preferences > Screensaver to see your photo albums shuffled.

This forum is for users to assist other users with a technical issue, if possible. As your post is not a technical issue I'm not sure what you're hoping for here.

If you want to make a feature request:

https://www.apple.com/feedback/photos.html

You know, it may also be the case that Apple don't see this feature as one they want to add. There are other apps. Search on the App Store.

.I am looking to see if there is a feature on Photos for random shuffle I have missed or someone has a solution to my problem

I've read and reread your first post several times and try as I might I son't see any such question in there.

Now I can't even go back to Mojave...they trap you once you upgrade. 

What's stopping you?

You need to wipe the disk and then install it. You can't install it over 10.15. Burt the best way is to restore the back up you made before upgrading. (You did make a back up, right?)

Hi Old Toad.

I downloaded your script for shuffling photos in a slideshow, however I cant see the option in the slideshow to run in shuffle mode.

Can you point me to it?

Regards

Darren