dvb

This isn’t needed anymore. You can configure exceptions for RFP, for example:

defaultPref("privacy.resistFingerprinting.exemptedDomains", "*.foo.com,*.bar.com,*.foobar.com")

ArchWiki: Hibernate on low battery level

This approach uses udev, so you don’t have to constantly check the battery level by yourself.

Yes, of course. You will have to adapt it to your time zone, as the German time zone is currently hardcoded. If I had known back then that I would be sharing this at some point, I would have tried harder. 😅

// ==UserScript==
// @name         Spoof Timezone
// @namespace    http://tampermonkey.net/
// @version      0.1
// @license      GPL-3.0
// @description  Overwrites the Date object to use the German time zone
// @author       dvb
// @match        *://*.foo.com/*
// @match        *://*.bar.com/*
// @match        *://*.foobar.com/*
// @match        https://webbrowsertools.com/timezone/
// @grant        none
// @run-at       document-start
// ==/UserScript==

(function() {
    'use strict';

    const originalDate = Date;

    function isSummerTime(now) {
        const month = now.getMonth() + 1; // January is 0, so +1
        const day = now.getDate();
        const hour = now.getHours();

        if (month > 3 && month < 10) { // Summer time is from April to September
            return true;
        } else if (month === 3 && day >= 29 && hour >= 2) { // Last Sunday in March at 2 o'clock
            return true;
        } else if (month === 10 && day <= 25 && hour < 3) { // Last Sunday in October at 3 o'clock
            return true;
        }

        return false;
    }

    function getGermanDate(...args) {
        const now = new originalDate(...args);
        const germanTimeZoneOffset = isSummerTime(now) ? -120 : -60; // German time zone is UTC+1 (+2 during summer time)
        if (args.length === 0) {
            return new originalDate(now.getTime() + (now.getTimezoneOffset() - germanTimeZoneOffset) * 60000);
        } else {
            return now;
        }
    }

    // Overwrite the newDate function
    const newDate = function(...args) {
        return getGermanDate(...args);
    };

    // Copy the prototypes and static methods
    Object.setPrototypeOf(newDate, originalDate);
    Object.setPrototypeOf(newDate.prototype, originalDate.prototype);
    for (const prop of Object.getOwnPropertyNames(originalDate)) {
        if (typeof originalDate[prop] === 'function') {
            newDate[prop] = originalDate[prop].bind(originalDate);
        } else {
            Object.defineProperty(newDate, prop, Object.getOwnPropertyDescriptor(originalDate, prop));
        }
    }

    // Overwrite Date objects
    Date = newDate;
    window.Date = newDate;
})();

I have a similar requirement and use a self-written script in Tampermonkey, in which I falsify the wrong time (GMT) to the correct time just for websites I have previously defined. Specifically, I overwrite the newDate function on these.

This means that Librewolf always displays the wrong time (GMT) by default, except for websites I want to have the correct time (which just are a few) without the need to disable RFP.

I feel the same way. Most of the feedback on your post seems to be from newbies who like it, so maybe we should start a new community for us advanced folks instead of referring everyone to !linux4noobs@lemmy.world.