If you’re hunting for legit places to read 'Blue Lock', the safest bet is to go straight to Kodansha and major ebook retailers. Kodansha publishes the manga, so check the official Kodansha USA channels and the K Manga app/website where available. They often have the newest volumes and official English translations. Beyond that, you can buy digital volumes on Amazon Kindle, comiXology (which syncs with Kindle in many regions), BookWalker, Google Play Books, and Apple Books.
Libraries are a surprisingly great option too — apps like OverDrive/Libby and Hoopla sometimes carry licensed manga volumes, so you might be able to borrow 'Blue Lock' for free depending on your local library’s catalog. Prices and regional availability can vary, so if a chapter or volume is missing for you it’s often just a geo-rights thing. I try to buy a volume every so often to support the creators; it feels good knowing the team behind 'Blue Lock' gets paid for their work.