It depends on whether the link is designed to stay in the same tab or to open a new window. Firefox has a separate preference for each, and only the one for "same tab" is on the Options page.

Give this a try:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste tabs and pause while the list is filtered

(3) Double-click the browser.tabs.loadDivertedInBackground preference to switch it from the default value of false to true -- the line should turn bold

Does that help?

Since there are a number of similar-sounding preferences, here is my understanding of when they apply:

• browser.tabs.loadInBackground => when you open a regular link in a new tab using Ctrl+click (or right-click > Open in a New Tab)
  • default = true, do not make the new tab active
  • In the Options dialog/page, this is controlled by the "When I open a link in a new tab, switch to it immediately" setting.

• browser.tabs.loadDivertedInBackground => when you divert a script-generated new window to a new tab using Ctrl+click, or when a page uses the target attribute to launch a link in a new window and you divert it to a new tab
  • default = false, make the new tab active

• browser.tabs.loadBookmarksInBackground => when you load a bookmark in a new tab using Ctrl+click (or right-click > Open in a New Tab)
  • default = false, make the new tab active

My main issue was when I Ctrl left clicked on a bookmark and it kept opening to it. That last option, browser.tabs.loadBookmarksInBackground, is the one that did the trick. It was on false but setting it to true fixed it. Thanks!