Something we already knew, but that’s now written down by Adrian Roselli in a nice post:
Regardless of what accessibility conformance level you target, do not arbitrarily open links in a new window or tab. If you are required to do so anyway, inform users in text.
Great to see that the statement is backed by the Web Content Accessibility Guidelines (WCAG):
WCAG Link targets fall under Guideline 3.2: Predictable, and state that web pages must appear and operate in predictable ways. Specifically, Success Criterion 3.2.5: Change on Request states that changes of context (such as new pages or windows) must be initiated only by users and that users can disable them otherwise.
And if you do need to use a new window/tab also add rel="noopener noreferrer" for security reasons.