I wonder if there are any alternatives to BetaFlight. If there are any alternatives, what are their advantages and disadvantages?
Among open-source options, Emuflight, INav & 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.
Yes, there are. For freestyle and racing, there are EMU Flight, FlightOne, and Kiss which are the most popular. If you fly using GPS you may want to consider INAV.
Here I will discuss the advantages/disadvantages of each when compared to Betaflight:
KISS: Advantages - Very simple interface without a lot of confusing options. The defaults are very good for 5-inch quads. The disadvantage of Kiss is that it has a smaller user base than Betaflight and it may be harder to find help from the community when you need assistance. Kiss hardware, flight controllers and ESCs often times cost more than their betaflight and FlightOne counterparts.
FlightOne: Advantages - The new FalcoX firmware is very easy to set up on your quad using the graphical OSD wizard. No computer necessary. The software has many presets from which you can choose to find which may work best for your quad. The disadvantage of FlightOne is hardware availability. Often times their FCs and ESCs aren't available. If you experience failure you may wait a while for a spare ESC or FC.
EMU Flight: Advantages - EMU Flight is a fork (a derivative of BetaFlight). Their goal is to focus on flight handling as opposed to Betaflight which appears to focus on features. EMU Flight is very good for those who fly whoops or sub 4 inch (prop diameter) quads. They use innovative filtering which is beyond the scope of this discussion. Disadvantages, EMU Flight is one of the smaller communities so getting help may take a while.
INAV: Unfortunately I do not have any experience with INAV. 2. List item