As above, I'm wondering if the characters on the show "Earth 2" from the 1990s ever actually referred to their new planet as "Earth 2", or if that was just a catchy title?
A quick scan through the show transcripts shows that they didn't refer to it as "Earth Two" (in-universe) at any point and that the planet in question is always referred to by its correct name, G889.
"We're here to settle this planet."
"Which planet? G889."
"Martin, I assume you have no idea what your friends on level six have planned for us tomorrow."
"Well, they're releasing us to planet G889."
That being said, graffiti and tattoos are seen with the words "E2" on them
We—” Her voice died in her throat as an image formed on the chamber floor at their feet, a design emerging out of the hard-packed earth. For a moment it was confusing, like a swirl of graffiti, but then it became chillingly clear: “E2.” Completely confounded, she stared in amazement as dirt poured away from the design, leaving it clean and precise against the background.
Earth 2: Official Novelisation
with the implication that certain minority groups view this planet as "Earth 2" (or possibly "Eden 2")
Alternative likely contenders for eventual renaming would presumably include Eden or New Eden (after the 'Eden Project')
"G889 was supposed to have been Eden. Uninhabited, ready for the taking."