Man, this question takes me back to when I was desperately trying to find this thing. Wandering the web for the web novel is honestly part of the whole experience. For anyone just starting, it's important to know that 'The Beginning After the End' started as a web novel on Tapas, and that's still the official, legal home for it. Tapas uses an ink system, but they have a solid free-to-read model with daily passes and first few chapters free. That's where I read the first three volumes. The writing there is the author's original version, which is actually the web novel, not a light novel adaptation.
I know some folks get antsy about the slow unlocks and look for aggregator sites. Those sites are everywhere if you search the title with 'read online', but I have to say, they're a mess. I tried a few and the formatting was janky, the chapter order was sometimes wrong, and the ads were straight-up malicious. You might get a few dozen chapters ahead for 'free', but you're also not supporting the author, TurtleMe. Plus, those sites often host fan translations of the light novel, which is a different, officially published adaptation in Japan. It gets confusing, so sticking with Tapas keeps everything straight, even if you have to pace yourself. After those first free chapters, I just settled into checking the app once a day to use the free passes; it became part of my routine.