I attached a test.
If the underlying RandomGenerator returns 0.0, then nextLong returns Long.MIN_VALUE, although the lower bound is Long.MIN_VALUE+1.
The javadoc of RandomGenerator#nextDouble does not clearly define, whether the result includes the lower border of 0.0 or not.
In java.util.Random it clearly defined as included: "uniformly from the range 0.0d (inclusive) to 1.0d (exclusive)". And the existence of JDKRandomGenerator suggests, that RandomGenerator should have the same contract.
I tested with version 3.1.1 from mvnrepository