The original LazyDFU project page lists Minecraft support through 1.20.x. Searches for LazyDFU mod 1.21.8, LazyDFU mod 1.21.10 or newer versions therefore need a different verification path: current results can point to separate unofficial ports.
Original project range stops earlier
The original LazyDFU release history does not present 1.21.x as part of its maintained line. That means a 1.21.x file should be evaluated by its own project page rather than by assumptions based on the older repository.
Unofficial ports can support more loaders
A separately maintained “LazyDFU Reloaded” project has advertised newer 1.21.x support and multi-loader variants. That is useful context, but it remains a different project with its own maintainer, metadata and risk profile.
How to verify a 1.21.x result
Check whether the page explicitly says unofficial or reloaded, confirm the exact game version, loader and environment, then review release notes. Avoid files mirrored without clear provenance.
Do you need it on modern Minecraft?
Because Minecraft’s DFU initialization was already improved in later 1.19.x versions, the performance value of a LazyDFU-style patch can vary. Benchmark rather than assuming the older startup gains carry forward unchanged.
Related next step
Use the compatibility information above before choosing a download. If you only have the supplied master.zip, remember that it is source code rather than a normal mods-folder JAR.