First three chapters with a fresh look on how to work with AST using functors and natural transformations:
https://muratkasimov.art/Ya/Tutorials/Lambda-calculus-interpreter-1/
https://muratkasimov.art/Ya/Tutorials/Lambda-calculus-interpreter-2/
https://muratkasimov.art/Ya/Tutorials/Lambda-calculus-interpreter-3/
Next ones are in progress: tracing variables, de Brujin indices and β-reduction.