Been busy and it's taken a while to get back here, but many thanks for the help.
re. asking about "Beginning a video automatically & 2 play icons"
I've never encountered the "two play icons" phenomenon.
... there's a reason why browsers do their best to block video autoplay.
It's because site visitors hate it. I don't use it in any of my own albums, and I've been sorely tempted to remove it from my skins. It's a fairly aggressive thing to do.
You're ahead of me as I use a still older macOS 10.14.6, but I don't think that's a problem. Looking at a video again, I think I can explain the two icons phenomenon:
The first play icon is the inner or embedded video player. The second or outer play icon refers to the album and it's potential slideshow.
re. controlling "animated GIFs"
For me, an animated GIF is always animated in all browsers, in both Windows and macOS. There's no such thing as "starting" an animated GIF. There's never a "play" icon...
Good point, I agree animated gifs play quite well in jAlbum and I see I misspoke on that "play" icon. I was probably thinking of the play once vs loop options when I create them in photoshop. Looking at one of my gifs again:
there is a play icon below the gif, but it is not the gif's, it's the other one that refers to a possible album slideshow.
None of this would be confusing for you or me..., but I do have even some web-wise visitors who get confused: e.g. by navigating thru a hierarchy of album folders, by seeing a matrix of thumbnails and sometimes not even realizing one can usually open an image and proceed through the album for the best experience. Or possibly some are aware of using the lightbox, don't find the photos interesting, and are just sparing my feelings, LOL. I do find visitors (in my case these are mainly family and friends) are sometimes confused about things I take for granted. On the other hand some with art school backgrounds who are now designers appalled if there is too much navigational aid. And typically neither type are good at or interested in reading an info or help page. I-like others-aim for a some kind of compromise.
So do realize that I might consider trying out and experimenting with some features that I might end up not using.
Thanks for your helpful suggestion to convert all GIFs to videos. No problem. That standardization might make a lot of things easier in the long run.
Re. "automatically open the first image, perhaps after a slight delay?"
No. ... that's another one of those things that I find aggressive, and I detest it when I run into it in albums made with other skins.
Ok
5. After opening an album, is there any way to automatically start the Slideshow?
No. Again, aggression. In fact, I can barely resist the urge to get rid of timed slideshows in my skins entirely. As a site visitor, I want to decide how long I look at each image. I don't want the album creator forcing his choices on me.
Ok
re. "Is there any way to place a play control icon ▶ on the index page of an album"
No. That's another one of those things that I could probably do, but since I hate timed slideshows,
Ok.
You would probably be surprised to find that I agree with most of your sentiments regarding automation. I don't hate and detest it as you claim to, but I would recommend that anyone designing their album site try to let the user control things and avoid automatically starting things to the greatest extent possible. I would not advise this so very aggressively as you.
There may be some album creators who are neither ignorant nor misinformed, yet still have a reason to offer some automations or accommodations to visitors. For example in iPhone (I realize you do not have one of these) settings, a section called "Accessibility" offers a number of features which though-not useful to all-can sometimes benefit folks with certain vision, motor and other challenges.
I have a father in his nineties who bought and mastered an iPhone enough to stay in touch over a couple thousand miles during covid quarantine. He's not an expert and has trouble with tapping or clicking on things. For some reason seniors often seem to stab at rather than gently tap, for example. He has more trouble the more navigation he has to do via tapping or clickiing on small areas on a screen. He might possibly be better accommodated by certain automations. It seems reasonable for some of us to be curious and inquire as to what sort of automation features are available.