54% of Wikipedia pages contain at least one link in their “References” section that points to a page that no longer exists.
My impression was/is that over the last years/decade Wikipedia made efforts to/switch to not linking directly but extending direct links with (dated) Web Archive links or using Web Archive links directly (dated as "sourced from this in this state; which protects against upstream edits too).
The Web Archive "Wayback Machine" is a project from archive.org, which does much more in archiving and accessibility efforts. An alternative service for websites is https://archive.ph/.