I have an unlisted version of the addon. It’s obviously, that some users will prefer to stay on FX 56, after the 57-th version is released, so I would like to ship both legacy and WebExt version as simpler, as it’s possible. Can I put them into one XPI, then sign it, so old Firefox will unpack it, and choose the legacy version, and the new Firefox will find inside the XPI everything required for the WebExt version?
Don’t think that is possible. If you have an unlisted extension, why not make 2 with different uuids. Also you can upload them with different max ff versions.
The answer is installer. It does not know the version of Firefox, so I’ll have to install both versions in hope, that Firefox chooses appropriate (another one still will be visible, but disabled - that’s just one more confusion).
It’s not possible to have both in one package.