Cannot access “about:config” in Firefox for Android beta / Firefox Preview / Fenix


I’m trying to access about:config but all I get is an error message saying “Cannot Complete Request. Additional information about this problem or error is currently unavailable.”

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The text in the address bar after trying to load about:config says

resource://android/assets/low_and_medium_risk_error_pages.html?&title=Cannot%20Complete%20Request&button=Try%20Again&description=%3Cp%3EAdditional%20information%20about%20this%20problem%20or%20error%20is%20currently%20unavailable.%3C/p%3E&image=&showSSL=false&badCertAdvanced=Advanced%E2%80%A6&badCertTechInfo=%3Clabel%3ESomeone%20could%20be%20trying%20to%20impersonate%20the%20site%20and%20you%20should%20not%20continue.%3C/label%3E%20%3Cbr%3E%3Cbr%3E%20%3Clabel%3EWeb%20sites%20prove%20their%20identity%20via%20certificates.%20Firefox%20does%20not%20trust%20%3Cb%3Eabout:config%3C/b%3E%20because%20its%20certificate%20issuer%20is%20unknown,%20the%20certificate%20is%20self-signed,%20or%20the%20server%20is%20not%20sending%20the%20correct%20intermediate%20certificates.%3C/label%3E&badCertGoBack=Go%20Back%20(Recommended)&badCertAcceptTemporary=Accept%20the%20Risk%20and%20Continue

I’m using Firefox 79.0.0 (Fenix) on a Samsung Galaxy S10+.