I did a little burrowing, and I now see what IAbot should do:

it should expand the shortcut archive-url, extract the original URL, and add a cite template with both url= and archive-url, like this

Before IAbot:

<ref>https://archive.md/wip/j7fYr</ref>

After IAbot:

<ref>{{Cite web |url=https://www.rte.ie/news/courts/2021/1221/1268045-ikea-woman-claim/ |title=Archived copy |archive-url=https://web.archive.org/web/20211222031449/https://www.rte.ie/news/courts/2021/1221/1268045-ikea-woman-claim/ |archive-date=22 December 2021}}</ref>

IAbot already has the code to expand an archive.today shortcut: see example 1 and example 2. The code is at line 3105 of Core/APII.php: https://github.com/internetarchive/internetarchivebot/blob/e094a56cebf9fe94d01f1d47e59c10fc57b01d79/app/src/Core/APII.php#L3105

All it needs is a few extra line to grab the original URL from the expanded archive link.