Thanks for your contributions!
I would rather go only to the Python coding option as last resource. It´s great having a link to an example here, thanks!
Kiwi!3D and Concha look great, but they seem intended for shells analysis so I think they won´t work with trusses.
By the way, Kiwi directly uses NURBS as basis functions for the Finite Elements. Hence, meshing of CAD models for analysis is avoided. Scan&Solve also avoids meshing stage for solids, but using a different strategy.
K2Engineering is the only one (besides Karamba) that considers buckling. However, it obtains the buckling load factor from a nonlinear load-displacement analysis (it should be slow but accurate). In any case, it is free and has beam elements, so I will try!
I´ve already tried Karamba, and it is a really good plugin. Definitively, I will invest the 30 € in the educational version as soon as possible. Only cross-section optimisation and buckling calculations (mainly) require buy. The free version is not restricted at all for most static and modal analyses.
Any other FEA tool intended for trusses and buckling?