Since the recent upgrade to gerrit 3.9 (thanks for doing it!), all the links in the "related changes" section can no longer be opened in a new tab, by either middle-clicking or ctrl-clicking them. For example, see change r1040191 which has a relation chain as well as changes with the same topic.
Note that the link can be opened in a new window via shift-clicking, and I can also right-click and choose to open the page in a new tab, but the former is not what I want, and the latter is inconvenient.