Setup GDK on MacBook ruby blocker

Welcome, I’m trying to setup GDK locally to start on Hackathon issues, but seems ruby blocking me.

After arriving to gitlab-development-kit wpplumber$ bundle install it gives the error below:

Fetching gem metadata from
Resolving dependencies...
Could not find compatible versions

Because irb >= 1.6.4 depends on Ruby >= 2.7
  and Gemfile depends on irb ~> 1.7.0,
  Ruby >= 2.7 is required.
So, because current Ruby version is = 2.6.3,
  version solving has failed.