The easy way is to use Firefox browser.

Log in to Groups.io, the group, the wiki using Firefox.

Open the first page of the wiki with links you wish to check.

In Tools in Firefox's menu, click on Check Page Links.

It will check the side bar too of Groups.io but it is still quick and effective. 

If you are unfamiliar with the process of installing the extension, Wiki Link Checking explains it step by step