title_body: Are there any alternatives to BetaFlight? I wonder if there are any alternatives to BetaFlight. If there are any alternatives, what are their advantages and disadvantages?
upvoted_answer: Among open-source options, Emuflight, INav &amp; Ardupilot (different focus) Butterflight (mostly defunct), Raceflight (mostly defunct).  There is still Cleanflight and Baseflight, which are the shared lineage for Betaflight, Emu, Butr, and others.
  Of these, EMU has an EKF (Enhanced Kalman Filter) variant of filtering, and also in older releases captures a lot of the 'goodness' of BF 3.5.7 filtering with a few PID adjustments that some pilots prefer for feel - and is now where Project Mockingbird does custom whoop tune development.
  
  FlightOne, especially FalcoX adds a lot of ease of use for OSD configuration, and on most setups the stock tune out of the box or selected from a short list of defaults will fly really well.  Require FL1 FC or FL1 license on specific F411 targets (at the moment) - FL1 makes great ESCs if you can get ahold of them.
  
  KISS is also a closed source, with mostly one source of ongoing development, but provides impressively good flight performance as well.  Needs KISS FC to work, I do recommend other ESCs.
  
  For closed source options, the biggest downside is cost and need to re-learn some of the approaches if you're familiar with Betaflight already.
  
  The biggest feature-set of Betaflight lies in the RPM Filtering capability (which in my experience can make cheap builds outperform most people's expensive stuff), although for many users without a background that makes the tuning process very accessible, the 3.5.7 builds of BetaFlight will fly better in stock or near-stock tunes.