As Discovery enters the docking area, they come across two starships: one is the USS Voyager, NCC-74656-J, the eleventh starship to bear the name. The other starship is the USS Nog, NCC-352070. The Nog is named after the character of Nog from Star Trek: Deep Space Nine (1993) who was the first Ferengi in Starfleet. The actor who played Nog (Aron Eisenberg) passed away September 21, 2019 from heart failure. The appearance of the USS Nog is a tribute to the late actor.
When Discovery reaches Starfleet headquarters, one of the bridge officers says some of the ships are composed of neutronium alloy, based on a rare, dense mineral only found in the cores of neutron stars, which producing artificially was only theoretical in the 2200s. This is a reference to Think Tank (1999), when the USS Voyager encounters a group whose ship's hull is composed of neutronium alloy, which is stated to be beyond the abilities of the Federation and the Borg.
As Discovery enters the area of Starfleet Headquarters they encounter U.S.S. Voyager NCC-74656-J, the tenth starship (11th of that name) to be named after the titular Intrepid Class ship of Star Trek: Voyager (1995). Many observers have compared the third season of Discovery to Voyager, since both ships are "far from home".
The appearance of the USS Voyager, NCC-74656-J marks the first time in Star Trek history that a ship other that the USS Enterprise has received a legacy registry with a lettered suffix. Though ship names are often reused, registries up to this point have been wholly unique. The name USS Defiant, for example, was used for both a 23rd-century Constitution-class ship and two 24th-century Defiant-class ship, but the registry numbers (NCC-1764 and NX-74205) were completely different.
When Burnham, Saru and Tal enter Starfleet HQ, you can briefly see a holographic star chart. There is marker of a Kazon Clan Forum, a reference to Star Trek: Voyager (1995) (the Kazon were one of the first hostile species encountered in the Delta Quadrant).