Is the Andromeda Initiative Stuck in the Heleus Cluster?

The 600 year timeframe is consistent with the FTL speeds they used to move between stars within the same cluster in the previous three games. This is discussed at more length on SF&F SE here: How do they get to Andromeda so fast?

The innovations that lead to them being able to make such a long journey between the stars are the cryo pods, and the ODSY drive:

Standard ship drive cores build up static electricity, and require periodic discharge on a planet or at specialized facilities to prevent static from building to dangerous levels. With few such suitable discharge points in dark space, the ODSY drive core was developed for the arks long-haul journey to Andromeda.

I've finished the game and nearly every side quest, and never saw or heard anything that even vaguely implied that there might be mass relays in the Heleus cluster. On my first playthrough, during the opening scene, I saw something that I thought might have been a relay, but it was just the Hyperion ark ship seen out of context with no introduction.

Those facts, combined with ample dialogue indicating that the Initiative is stuck in the Heleus cluster for the foreseeable future, lead me to conclude that

• there are no mass relays in Heleus,
• they didn't use a mass relay to get to Heleus,
• and that they would need to fuel up and go back into cryo in order to leave the cluster.