The only buildable SDK for the LPC54605J512 device seems to be exclusively for the device/package: LPC54605J512ET180 (and no other packages). The BD100 package (and others) are not included in the options for the buildable SDKs but should be. Also isn't it intended that the NXP Boards that support the family of a device could/should be able to be included in the SDKs built for IC members of the family that those board models are used for even if the selected IC is not the family member used in the board -- i.e. the buildable SDK for the LPC54605J512 device doesn't seem to be able to include support for the OM13092 LPCxpresso54608 board though that board (or similar) supports development for the family the 54605 is in. Or maybe it could/should be possible to include the IC family members in a Board based SDK built for the board and not just the exact IC used on that board.
The LPC54606J512 SDK in comparison includes support for the several packages the LPC54606 is offered in, though still not also the LPCxpresso Board for the family.
Also do the SDKs have to be different for the J256 and J512 memory variants of the device? Could it not be possible to build a SDK that includes support for all memory size / package options of an IC and perhaps also selected board(s) which support that IC's family?