[oasisaimlessly]

> If this is the current state of the art, are there generally-available/open-source libraries existing that implement this and practitioners use for this?

The authors of [1] do discuss and link to their own library in section 5.

However, in my experience, most people implement the math themselves rather than use any libraries (beyond e.g. Eigen).

> How did people use KF on physical objects before 2010?

The Multiplicative EKF (MEKF) was used since 1969 according to [3]. It's a hacky approximation of [1]. [1] is really just a generalization/unification of lots of application-specific hacks that were used before, including the MEKF.

[3]: https://ntrs.nasa.gov/api/citations/20040037784/downloads/20...