The two Galactica series occur in the same continuity.
Anders and his resistance group can't have been the only people who survived on the Colonies. The survivors gradually managed to rebuild their civilization until they were attacked by the original-series Cylons (who were created by a non-human race, as stated in the series) and went on an exodus of their own to find Earth. The two Galactica series are alternate continuities of each other.
Battlestar Galactica (1978) is the universe where the Colonials never created the cylons (however they do have the technology to do so - hence Muffet the robot dog). Instead of creating robots to fight their wars, their technological development focused on laser weapons."Alien" aliens exist in the classic universe, and don't in the reimagined universe. Also, the classic universe has colonies - lost and otherwise - where humans still exist.
Sire Uri never made it off Carillion.
Which is why he doesn't appear in the rest of the series. He was captured by the Ovions, and just as they were "preparing him for storage", the planet blew up.- Gee, the idea of that being true would just break my heart.
The Richard Hatch continuation novels ignore most of the filler episodes of the original series.
It is already established that Galactica 1980 never happened in this version of the continuity. Fans hated that show and Richard Hatch felt our pain.note The characters don't flashback much except to the events of Saga of a Star World,Lost Planet of the Gods, The Gun on Ice Planet Zero, The Living Legend, and War of the Gods. These five stories could be considered the core of the original saga at its bestnote . And they do reflect the producers' original purpose of the SOASW being followed by several TV movies. It was Executive Meddling that turned it into an hour long episodic series with a lot of filler episodes. But the novels never make conspicuous references to the Terra Arc (Greetings from Earth, Experiment in Terra) or the Planet of the Week episodes which recycled Westerns (The Magnificent Warriors, The Lost Warrior, The Long Patrol, The Young Lords). Then there are scientifically inaccurate episodes such as Fire in Space. Although not an unpopular episode, The Hand of God, due to it's ending, strongly suggests that there is no plausible reason for the Galactica's journey to continue for much longernote . Readers are left to their own imaginations to decide whether the filler episode events happened or not.