Aimy Canonical PRO v3.10.0 allows to use a document's <base> path as a canonical path.

Use <base> Path as a Canonical Path

You can now use the path of the <base> element for your canonical link tag as well. Under some conditions this allows to work around issues with overlong paths set for your canonical link tag.

If you experience issues with your canonical link tag, you may want to give this new option a try. But keep in mind it requires SEF URLs (search engine friendly URLs) to be enabled in Joomla!'s "Global Configuration".