There is no issue with canonical strings from what I’ve tested. I used the latest versions of our plugin and addon and tested them with Yoast SEO and RankMath, both in the latest versions.
As my colleague already specified in that ticket, TranslatePress doesn’t create canonical at all. Those are added by the SEO plugins probably, but they use the translations made with our product. You can create a new post, and translate its slug, then you will see in additional language, the canonical is translated also with the same string. Changing the slug of the original post, will not affect the translated slug, which will remain with the same translation, thus the canonical will remain with the same translation as well. Changing the slug translation will also change the translation of the page canonical in that specific language. There is no issue with canonical, at the time we speak.
However, slug translation is a paid feature, and the WordPress rules forbid discussions about these. In case you want to find more about SEO translation you are more than welcome to open a ticket on our website: https://translatepress.com/support/ask-a-presale-question/.
