A few updated Developer Resources related to SketchUp 2021.1:
SpeedUp - Ruby Profiler
SketchUp 2021.0 shipped with Ruby 2.7.1. Ruby 2.7.0 and Ruby 2.7.1 both contained a bug that affected the profiling capabilities in Ruby. This prevented tools such as RubyProf (That SpeedUp uses) to work correctly.
SketchUp 2021.1 ships with Ruby 2.7.2 that includes a fix for that bug.
We used the opportunity to make SpeedUp work on macOS, going back to SU2017.
- Works with SU2021.1+
- Works on macOS!
Get your profiler hat on and give your extension a speed boost! 
rubocop-sketchup
- Updated with support for 2021.1
SketchUp Ruby API stubs
https://rubygems.org/gems/sketchup-api-stubs/
- Includes 2021.1 features.