Does it install on Firefox? (And no, for the purposes of this question, Waterfox isn't Firefox)

If yes - problem with Waterfox. Don't blame me or this addon for not working. Blame Waterfox devs for screwing up the fork.

If it doesn't install in Firefox (non-dev), your Firefox profile is corrupted. Make a new one and try again.

Uploads to AMO are moderated and reviewed before being approved. When reviewers notice and point out something as trivial as two stray console.logs that I forgot to disable in prod, one would imagine they would also notice extension not installing. I'd probably also notice that.

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Edit: just tried out Waterfox. Things get a bit funnier than I first expected.

Turns out Waterfox uses the same profile as Firefox (and that you can't run both browsers at the same time). Which means that every extension that you install in Firefox is also available in Waterfox. (Extension itself seems to work with Waterfox if installed via Firefox).

All in all, you should probably file a bug report to Waterfox and attach this extension to it, because everything is correct and to spec on my end. I'm 90% certain it has something to do with Waterfox not reading manifest.json correctly.