We have myriad possibilities.

The painting’s installation elements — including a plastic vacuum tube filled with “alphabet dice” — hint at myriad possibilities. – Seattle Times

We have a myriad of possibilities.

Thanksgiving is almost here, and with it comes huge platters of delicious food, pies as far as the eye can see, candy dishes full to the brim, and a myriad of choking hazards that no one ever told you about. – Romper

Which one is it?

‘Myriad of’ is older than myriad with the noun,” [Prof.] Curzan explains. “Myriad comes into English in the 16th century when the word originally means 10,000, a specific number.” The word changed from referring to 10,000 of something, to meaning a countless number of something.

While ‘myriad possibilities’ is taut, succinct … ‘a myriad of possibilities’ is the original form. Either one is fine. Listen to this interesting discussion with Professor Anne Curzan at Michigan Public Radio.