Bitrot isn't as much a concern any more - we have data formats worked out these days, with well defined specifications and open standards (PDF/A), so basically as long as computers keep operating on the fundamental principle of bits and bytes, our documents will always be able to be read, and for virtually all popular data storage formats there is open source software that can, should the need arise, be run in an emulator.
In fact, future historians should have it easier to understand our times, given that machines can actually sift through data at speed and you don't need humans to tediously take and scan brittle paper, and a lot of data is replicated so often across the planet that even a nuclear war should leave at least one copy alive in contrast to earlier times where wars, fires and natural disasters would routinely wipe out entire nations' memories. (Doesn't stop people from trying though, just look at the book burnings in Ukraine committed by Russia)
The dark era IMHO more concerns pre-MS Windows computing and everything related to gaming. The former because a lot of data there (hole punch cards...) literally rotted away, the latter because of decades worth of homegrown architectures, all kinds of DRM, a lack of obligations for publishers to submit DRM-free copies and copies of the server backend code to national libraries, and the current "trend" towards e-stores for games instead of physical media.
