Keeping or observing the feasts is no longer a religious requirement though there is benefit from what the bible teaches about them.
We learn about the feasts in Leviticus 23, also book of Ester for Purim and Daniel / John 10:22 for Feast of Dedication. We study and commemorate these feasts celebrating what God has done in historical fulfillments, what He fulfilled in Jesus’ first coming, and prophetic of what Jesus will fulfill in His second coming.
We stick to what the bible teaches about these feasts and avoid unbiblical traditions that have grown around these feasts.
I say commemorate versus “observe”, as many of the feasts require sacrifices and ceremonies that are fulfilled in Jesus and those practices need no longer be carried out as a religious requirement.