I'd say you can and you should. Unless you're working in a Jira sweatshop, you have some slack in between tasks. To the extent you're hired as a professional and being expected to perform creative work, learning is part of the job description and it's fair to do some on employer time. Good companies recognize this explicitly, though I'm yet to be in one that would frown on people who don't just stick to solving tickets as fast as they possibly can.
