I'm being slightly facetious, but only slightly with this, but maybe not...as people who don't have a lot of mac experience may ask about these very machines.
These will not run MacOS 9 using the patches discussed, some may run it, but in emulation, or already do natively (no patches needed):
G5's (cpu differences...lack of drivers...I believe?).
m68ks (wrong cpu).
apple silicon (wrong cpu)
nubus ppc (no open firmware?).
603's and 604's (already do natively...no need for these patches. You should not run an "unsupported version of macos 9" on these, just use the stock release).
----
Working, but limits:
old world macs (with toolbox roms, not on disk) will be a little more difficult, but should be ok?
dual cpus are not made use of, as far as I know (incompatibility with mutliprocessing services?)
some chipsets and memory controllers are better supported than others.
If you see someone running MacOS 9 on their machine, and wonder about yours, you might check developer notes or documentation to see if your machine uses a similar chipset. If it does, you are probably in luck.
don't expect all io devices to work, most do or have workarounds, but the first thing you may see is graphics or audio not working well. Some of these are macos 9 driver issues, and not related to these patches at all.
If you have trouble with macos 9, consider trying System 7.6. That may sound crazy, but may help you diagnose why macos 9 is having trouble. System 7.6 is even more limited driver wise, but does work well on a machines like minis.
usb support is good, but many devices will lack macos 9 drivers. If you have usb 2, you will probably need to take care of that separately, or it will just act as usb 1.
For some g3 or g4 accelerators, you may or may not need to use an extension to enable caches?
Not all your memory may be visible to macos 9 due to a design flaw. There are some workarounds for this, but they are not perfect.
If you have trouble, remove all unneeded cards or devices and try again.
Some exotic hard drive controllers may or may not work, or, if they do, may not have all their features supported?
----
I've put question marks on things I wasn't personally sure of.
The above may not be FULLY entirely correct, but has some good guidelines.
Feel free to quote or use, I know some of it may be wrong, so correct if you feel the need to do so.