Right now there is a bit left to be desired when it comes to lemmys accessibility features, but it’s a good idea to be mindful of the fact the fediverse and its platforms tends to have pretty universal accessibility features that will likely come to lemmy sooner rather than later
This is only applicable to inline pictures on text fields. Posting images/videos does not have an alt text field. The closest you can get is using the text field of a post as an alt text field.
Hmm, you’re right. I was sure there was a separate field for that when posting images, but I must’ve been confused.
You can still use online images to submit posts through Mastodon, though, I believe.