In Red Hat 8.0, the installer detected the serial mouse automatically. In Red Hat 9, the detection failed.
Well I had the same phenomenon switching from RH7.3 on an IBM Thinkpad a31p, where kudzu didn't detect my trackpoint any more (which is a shame when sitting on a train, having no other pointing device). Well, XFree can be configured to use multiple mice, as could gpm, if the start script was not buggy in RH9.0. this leads to the next problem with gpm. which could not be configured to use two mice at the same time. I have a workaround for that in the annotation of bug: 84310 thanx.
The installer does not currently support detection of serial mice (and that is unlikely to change), as such, closing this out.