works for me

autoconfig.js

@@ -0,0 +1,36 @@
+// based on https://support.mozilla.org/en-US/questions/1378404#answer-1510431
+try {
+	const hotkeys_to_disable = [
+		'openFileKb',
+		'key_savePage',
+		'printKb',
+		'key_close',
+		'key_closeWindow',
+		'key_toggleMute',
+		'key_reload',
+		'key_reload_skip_cache',
+		'key_quitApplication',
+	];
+	new (class {
+		attributes_to_remove = ['command', 'key', 'modifiers', 'oncommand', 'data-l10n-id'];
+		services = globalThis.Services || ChromeUtils.import('resource://gre/modules/Services.jsm').Services;
+		re_href = /^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i; // whatever, I'm not refactoring this
+		constructor() { if (!this.services.appinfo.inSafeMode) this.services.obs.addObserver(this, 'chrome-document-global-created', false); }
+		observe(w) { w.addEventListener('DOMContentLoaded', this, {once: true}); } // Tempting to check location here, but we don't have it yet
+		handleEvent(e) {
+			const D = e.originalTarget, W = D.defaultView, L = W.location;
+			if (!L || !this.re_href.test(L.href)) return;
+			if (!W._gBrowser && !W.Tabbrowser) return; // https://bugzilla.mozilla.org/show_bug.cgi?id=1930654
+//displayError('debug', '[ ' + L.href + ' | ' + W.document.getElementById('key_reload') + ' ]');
+			hotkeys_to_disable.forEach(n => {
+				const k = W.document.getElementById(n);
+//displayError('debug', '[ ' + n + ' | ' + k + ' ]');
+				if (k !== null) this.attributes_to_remove.forEach(a => k.removeAttribute(a));
+			});
+		}
+	})()
+} catch (e) {
+	displayError('hackmaster', e);
+}
+
+lockPref("hackmaster.autoconfig.loaded", "a miracle, really");