You should be able to transit FRA if you meet the entrance requirements to enter your final destination, your trip is for a "worthy purpose" ie not for tourism AND you're not overnighting outside the airport. Be prepared for lots of questions and have everything documented (in writing). Evidence of a negative COVID test is also advised.

This page is in German but google translate is more or less accurate. See the section on "when is it mandatory to enter Germany".

https://www.bundespolizei.de/Web/DE/...faq.htmlhttp:/

Also you must satisfy the regulation of the German province (Hesse) (also in German):

https://soziales.hessen.de/gesundhei...er-einreisende

My experience has been most issues occur checking in with AC in YYZ . I was advised by a duty manager in June (before Canadians were taken off the restricted list) this is the site they consult when determining ability to board. A passenger had to meet the entrance requirements for every stop:

https://www.iatatravelcentre.com/world.php

I travelled via FRA on Nov 6/7th, AC had not yet updated their system to reflect new requirements for Canadians travelling to/through the EU so it took almost an hour to check in.