Looking for the official sources is something most people skip, but it's honestly where I've had the best luck lately. A lot of the big publishers like Shueisha have their own free platforms—Shonen Jump's app lets you read the first and latest three chapters of so many series for free, no subscription needed. The translations are solid, the site doesn't bog down with pop-ups, and you're actually supporting the industry in a tiny way. I got into 'Chainsaw Man' that way, just catching up on the recent chapters every week, and it felt way less chaotic than chasing down random scanlations.
For completed series or older stuff, I tend to lean on library services now. My local library uses an app called Libby, and I was shocked at how much manga they have digitally. You link your library card, browse, and borrow it just like a physical book. The selection can be hit or miss depending on your library system, but I've found full runs of things like 'Death Note' and 'A Silent Voice' on there. It's a legal, ad-free option that a lot of folks forget exists. The wait times for popular titles can be a drag, but putting a hold on something feels like the digital equivalent of that old thrill of finding a volume on the shelf.
The aggregator sites everyone mentions are still out there, but the quality has dipped so much. The ad overlay is insane, pages load out of order, and you're never sure if the translation is some botched mess from five years ago. I'll only resort to those if I'm desperately trying to find a specific, obscure one-shot that isn't available anywhere else legally. Even then, it feels like digging through a digital junkyard—you might find the part you need, but it's not a pleasant experience.