I would not assume that 85 was the first version to break this. I suspect it was broken on Firefox 69 or so as part of the Fenix rewrite or as part of the Fennec code removal project (bug 1582218). If someone wants to manually bisect there are builds on https://github.com/mozilla-mobile/fenix/releases/ Mozregression won't work in this case because full Fenix builds are not supported, just the lightweight Geckoview Example browser.
Bug 1697647 Comment 16 Edit History
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I would not assume that 85 was the first version to break this. I suspect it was broken on Firefox 69 or so as part of the Fenix rewrite or as part of the Fennec code removal project (bug 1582218). If someone wants to manually bisect there are builds on https://github.com/mozilla-mobile/fenix/releases/ Mozregression is unlikely to work in this case because full Fenix builds are not supported, just the lightweight Geckoview Example browser.