your TiBook will also support OS X 10.4.11, the final incarnation of Tiger, but I'm not certain how well that will run on a 550MHz machine. If you follow Rick's advice and upgrade to 1 GB RAM, Tiger should run fine. I ran it on my G4 DP 450 (slower processor than your TiBook) and it was very fast.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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