The DTM mode will accept the commands outlined in the Bluetooth Core Specification 5.0, Vol 2, Part E, Section 7.
The direct test mode commands, outlined in Vol 6, Part F, are also accepted.
There are Maxim-implemented Vendor Specific commands that would also be useful in this context:
#define HCI_OPCODE_VS_SET_BD_ADDR HCI_OPCODE(HCI_OGF_VENDOR_SPEC, 0x3F0)
#define HCI_OPCODE_VS_SET_TX_POWER HCI_OPCODE(HCI_OGF_VENDOR_SPEC, 0x3D4)
The VS_SET_BD_ADDR command accepts an 8-byte address for the new address of the device.
The VS_SET_TX_POWER command accepts a single byte.