The 'new' non-clone stormtroopers helmets are an homage to Ralph McQuarries original designs.
The design of Echo's ship the Remora is based on the Meson Martinet, the Crimson Corsair's pirate ship partly visible in Star Wars: Episode VII - The Force Awakens (2015) and fully realized in The Mutiny (2020).
The planet Balmorra first appeared in the 1994-1995 comic book series Star Wars: Dark Empire II. It is also featured in the video game Star Wars: The Old Republic (2011), Balmorra was a key world during the war between the Old Republic and the Sith Empire due to the planet's many battle droid factories. Balmorra was mentioned by name in Shadow of Malevolence (2008) but makes its first onscreen appearance here.