Quick question that came up last night.

One PC cast Confusion. A Legendary Creature failed their save. Before there turn came up we hit Init 20 for a Lair action. They had not reached their first turn after casting, so they had never rolled on the Confusion table.

The Monster Manual errata / later printings state about Lair Actions:
On initiative count 20 (losing all initiative ties), it can use one of its lair action options. It can’t do so while incapacitated or otherwise unable to take actions. If surprised, it can’t use one until after its first turn in the combat

The Confusion spell states:
An affected target can't take reactions and must roIl a d10 at the start of each of its turns to determine its behavior for that turn. Most (but not all of the effects) either deny an action or specify what it must be, but a 9-10 allows them to act normally.

How would you rule the interaction between the Lair Action limitation about while incapacitated and the Confusion spell?

If you can, let me know if this is your reading of RAW, how you'd personally adjudicate it at your table (which may be based on RAI/RAF/whatever) or both.

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