Can I buy the iPhone SE unlocked / without a contract?

Yes, most iPhone SE models are unlocked.

Buying an iPhone SE from Apple with any carrier selected, and paying with a one-time payment or Apple iPhone Payments delivers an unlocked device.

The iPhone SE can also be purchased "SIM-free". This means no carrier SIM card is included, the iPhone SE is unlocked, and a SIM card from any supported carrier can be used.

The only exception is iPhone SE units will be locked to AT&T when an AT&T installment plan is selected at checkout.