@Rokosun @frankie
Short answer: Yes you can add Alt-Text to images on Friendica, here's how to do that - wiki.friendi.ca/docs/image_des…

Long answer:
So in friendica they use a markup language called BBCode for their posts, everything including images, videos, etc are referenced using its syntax. You don't have to learn all the syntax yourself because there are buttons for simple things like adding images, underline, italic, bold, quote etc. Adding descriptions to images are also supported, here is info on how to do that - wiki.friendi.ca/docs/image_des…
Unlike mastodon, Friendica also supports adding inline images to your posts, so it makes sense to write your image descriptions inside the BBCode tag for images.

I'm writing this post from my friendica account, and here's an example of image with description: