Translations of AHRS-algorithms found at: https://github.com/tyrex-team/benchmarks-attitude-smartphones/blob/master/src/Filters/Implementations/QMichelEkfExtmagWtRep.m
starting at the Filters folder there
Note I currently have the updated C# translation locally ...but I can upload them if there is any interest (raise an issue for it)
In the end it was hard to confirm translation was working, and in 2 algorithms that I think I managed to translate correctly - I could not see any big difference compared to system quaternion (iOS). You can visit the original Tyrex repo for more info.