Just wanted to draw people's attention to a couple of things: "There are a number of work-arounds being discussed in the community. These are not recommended as they may conflict with fixes we are deploying. We’ll let you know when further updates are available that we recommend, and appreciate your patience. (May 4, 15:01 EST)" >From the updates on the bottom of https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/
Second, that blog entry will supposedly be updated as things unfold, so it may be at least a semi-authoritative way to track what's going on.