Does blue Seraphine, Inspiring trigger if you move 3 units at the same time? manual move

Radiance rules aren't published yet. This uses the printed card and current rules only, and it isn't a ruling on the new mechanics.

Yes — it triggers, and you draw 1 card (not 3). Moving several units with a Standard Move is a single game action, and exhausting those units is the cost for it, paid simultaneously (Rule 144.3.c), so moving 3 units together is literally "exhausting three or more friendly units at the same time." The "once each turn" clause caps it at one draw regardless of how many units moved, and it's a triggered ability, so it goes on the chain and opponents can respond to it.

One caveat: all units in a single move must share the same destination (Rule 144.3.a), so no splitting the three units across battlefields in one action. Seraphine also has to be on the board at the moment the units are exhausted, and the move itself has to happen in your Main Phase during an Open State.