The phone number (323-244-5631) that Bosch lists on the forum actually connects to a voicemail box for "Harry Bosch"
Titus Welliver's oldest son, Eammon, plays a young Bosch in a flash back scene in Legacy and his younger son, Quinn, plays a young Bosch in flashback scenes in season three of Amazon Prime's original Bosch.
Maddie's fellow "boot", Paulina Calderon, is named after the actor that played Detective Jimmy Robertson on the original Bosch (2014) series, Paul Calderon.
Honey Chandler was only ever in one of the original Bosch books ("The Concrete Blonde").
In Michael Connelly's Bosch novel universe, Bosch and Mickey Haller, The Lincoln Lawyer, are half brothers. Presumably, because Amazon has the TV rights to Bosch, and Netflix now has The Lincoln Lawyer, the lawyer roles where the two characters crossover, now goes to Honey Chandler.