In my headcanon Tom was rotting in a Cardassian prison cell when Cardassia finally turned on the Dominion on Cardassia Prime. A trained Star Fleet lieutenant is a powerful asset in a battle. Seeing the Dominion as a worse threat to the Maquis interests than Cardassia, Tom convinced his jailers to free him in exchange for him fighting to defend Cardassia. The combined Alpha Quadrant forces succeeded in defeating the Dominion. While Cardassians would have wanted to re-imprison Tom, the destruction and chaos was too great and Tom was able to slip away and make his way back to a rim colony that supported the Maquis.

The colonists, aware of the sacrifices Tom made to defend them hid and housed him. These colonies were far off the radar of the Federation at this point, so there was no one in power caring what they did, including if the Federation discovered Tom’s whereabouts there. Tom had everything he could build a happy life with there, and a community that loved him. He could have lived there happily for the rest of his life…but that’s just not the temperament of a Riker, so he left the safety and comfort of that work and once again threw himself into the fire for a cause…

…but that is another story.