I've been opening some of my older Affinity Publisher 1.10.5 documents in Affinity Publisher 2.0.0
Most of them open fine. But some cause Publisher to crash.
As in past versions of Publisher, the work around is to copy the document to another directory and to open it from there. And then save over the original document.
However, this is an annoying bug, so it would be nice if it could be logged and fixed.