A key feature of interest is that we have continued to significantly revise our documentation. The Nonlinear Modeling section is now much clearer, and there are now integrated tutorials. If you have suggestions for how things could be further improved, please reach out.
Links to specific PRs are in the tag notes: Release v0.21.7 · jump-dev/JuMP.jl · GitHub
Thanks to all the contributors, especially those who contributed for the first time!