Cannot open "New user script" on Firefox Nightly Android

[bunglegrind]

In addition to #3112, I have another couple of issue (and probably they are related) that make greasemonkey completely useless.

Simply put, the option "new user script" is not working. It doesn't do anything.
Environment: Firefox Nightly latest (which is unfortunately the only way to install and extension not recommended) + Android 11 + OPPO A52

The error messages in the devconsole are quite useless IMHO, btw, the first one is:

TypeError: can't access property "sendRequestForResult", dispatcher is null

prompt resource://gre/modules/GeckoViewPermission.jsm:249
    openDb moz-extension://c9b95f4d-bede-487e-81b6-36ed2aae0a05/src/bg/user-script-registry.js:50
    installFromDownloader moz-extension://c9b95f4d-bede-487e-81b6-36ed2aae0a05/src/bg/user-script-registry.js:81
    onUserScriptInstall moz-extension://c9b95f4d-bede-487e-81b6-36ed2aae0a05/src/bg/user-script-registry.js:179
    <anonima> moz-extension://c9b95f4d-bede-487e-81b6-36ed2aae0a05/src/bg/on-message.js:34
    apply self-hosted:2715
    raw resource://gre/modules/ExtensionCommon.jsm:2414
    wrapResponse resource://gre/modules/ExtensionChild.jsm:218
    responses resource://gre/modules/ExtensionChild.jsm:187
    map self-hosted:221
    emit resource://gre/modules/ExtensionChild.jsm:187
    recvRuntimeMessage resource://gre/modules/ExtensionChild.jsm:369
    recvRuntimeMessage self-hosted:1175
    _recv resource://gre/modules/ConduitsChild.jsm:82
    receiveMessage resource://gre/modules/ConduitsChild.jsm:188