Using the Repeating Field / Gallery I'd like to show the Alt or Title text below the image (not just on hover).
Also the larger image on my example the Alt text never changes, i.e. only one of the image's Alt text is ever displayed. The thumbnails are fine and on hover display the correct Alt text.
An option would be to not use Blocks to create the slider and choose some JS slider library to help create one where you had more control, including the ability to show captions.
I did test the issue with the tooltip which shows the wrong title for the large image on all but the first image, and I'm reporting that as a bug. I'll let you know when there is news of a fix.
With the plugin update the slider (and gallery) functionality of the Repeating Fields / Gallery block got split out into their own blocks, and you should have been prompted to convert/update.
Did you do that?
The block generating your slider should now be a Slider block.
Now, I just did some testing before replying to you, and found that the tooltips seem to have disappeared altogether.
I'm sending that back to the developer.
The new Slider block also allows adding captions to static images, but not dynamic images (your original question), which makes no sense to me so I'm pushing to see if we can add that.