You should use archive.org or archive.today links.
The best way to influence the Domain Authority metric is to improve your site’s overall SEO health, with a particular focus on the quality and quantity of external links pointing to your site.
You can use the Wayback machine addon to easily get archived links https://addons.mozilla.org/en-US/firefox/addon/wayback-machine_new/.
And a bookmarklet for archive.today:
javascript:void(open('https://archive.today/?run=1&url='+encodeURIComponent(document.location)))
FYI, if you’re worried about archive.today going down and references being lost, you can manually leave in the original URL by adding https://archive.ph/o/ in front of any URL, after you archive it. IE: https://archive.ph/o/https://sh.itjust.works/post/26060585 will redirect to the archived page, if it exists.
Had a look at the relevent github issue and it seems that it simply back links each individual post to its originating instance so we unfortunatly dont get combined domain ranking for the fediverse as a whole just each post.