Mac OS 8.5: PowerBook 500 PPC Not Supported

From an Apple TIL file (#30818):

Mac OS 8.5 supports only Apple branded computers with a PowerPC processor that have not been upgraded from 68K with a PowerPC daughtercard. Apple computers that have been upgraded to PowerPC with a full logic board, such as a PowerBook Duo 280c to a 2300c, are supported.

PowerBook 500 Series computers with a PowerPC upgrade are therefore not qualified or supported with Mac OS 8.5. The Mac OS 8.5 installer will refuse to install on this type of computer and a Universal Install of Mac OS 8.5 will not boot the computer.