Order of photos are changed !

It will depend on the system version, if it is useful to invest work into the sorting of the photos in the shared albums.

The online version of the shared album might get rearranged, whenever someone is adding a comment to one of the photos, because this will change the "date added". If you are going to the throuble of posting the photos in a certain order, do not allow the subscribers to post or comment.

And since iOS 17/iPadOS 17 and macOS 14 Sonoma any subscriber can sort the Shared albums in Photos by the capture date of the items, so they may be seeing a different view of the album from the view we are using.

The most reliable way is also the most tedious: create the shared album with only the photo you want to see first, then add the others one at a time in the order you want them to appear.