Are you planning to use this firmware for a installation or a standard WISP setup?
SHA256: 4a8f2c1d9e3b7f6a5c4d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0 Ubnt Firmware Xw.v5.5.6 Download
Ubiquiti maintains an official download portal at dl.ubnt.com . The direct path for legacy firmware is: Are you planning to use this firmware for