The last really supported Flash for PPC was 10.1.102.64, but if it's for like Facebook or such, people have been fooling FB to think they have a later version installed.
Texas Mac Man's Flash hack/post...
Flash player 11.1 hack on PowerPC - https://discussions.apple.com/message/16990862
See in each Browser which version of Flash it thinks it has...
Or free 3rd party...
Flash Player version 10.1.102.64 is the last version available to PPC Mac users. However, this Flash version won't work for many videos on Facebook, YouTube and other sites. Adobe's latest version, 10.2.x or later, is only for Intel Macs. Adobe will not provide a newer Flash version for PPC Macs.
The message requesting that you download Adobe Flash Player takes you to Flash Player requiring an Intel processor. Doesn't work on a PowerPC processor. I found a hack, installed it & it works with Firefox, TenFourFox & Safari.
Download this http://www.steelbin.com/FPforFBPPC.zip to your desktop, unzip it, and replace the current Flash Player plug-in which is in your main/Library/Internet Plug-Ins folder, (not the user Library). Save the old one just in case this one doesn't work.
Hack Allows PowerPC Macs to Access Flash 11 Content
I used Texas Man's solution on my 17" G4 Powerbook, and it worked like a charm. My wife's 13" Intel MacBook (MAC OSX 10.5.8) also would not play episodes of Glee, getting the same "outdated Adobe Flash Player" notice, so I used the same procedure on that machine and it also worked just fine.
Thanks so much, Texas Tom. You made my day.
Now I can run MOG.com on my PPC with OS X Tiger 10.4.11.
For those who don't know, MOG is a music streaming service as good, or better than Spotify. Both the free and premium service streams in 320 kbps, where you have to pay for Spotify to get that.
I have a question, though:
Will this fix still work as Adobe keeps updating Flash Player? Currently they are up to version 12 and this fix works for Flash Player 11.