Several methods defined in core/rbs/unnamed/random.rbs are methods made available in Ruby through the extension library random.formatter.

$ ruby -e 'p Random.uuid'
-e:1:in '<main>': undefined method 'uuid' for class Random (NoMethodError)

$ ruby -r random/formatter -e 'p Random.uuid'
"21f9f77d-a378-4f6f-8ec6-f90dd17cb5ff"

We should define stdlib random/formatter and move the methods from core.
Moving from core to stdlib is an incompatible change.
We've had the same experience with stringio, so it should be a useful reference.

The random/formatter is an extension almost exclusively for securerandom, so the impact should be minimal.
Simply moving the method is also an option.