Since Android does not natively open FB2 files, you should install one of these highly-rated apps:

: A lightweight but powerful classic reader that is particularly popular among long-time digital readers for its "paper-like" settings.

: A popular Russian-language library offering a massive selection of books specifically in the FB2 format.

: A great English-language resource that supports multiple formats, including FB2, for hundreds of titles.

: Known for its deep customization options, visual themes, and support for almost all ebook formats.