So with MacTubes' last update being two-plus years ago, this would appear to be the end for this venerable app and saver of countless old Macs. The thing I'll miss most is its local playlist feature, where you could save playlists to your hard drive and have them display with videos' thumbnails in MacTube's browser. I haven't seen this feature on any other Youtube app.
You may notice, though, one Youtube downloader conspicuously absent from the list of broken apps, and that's youtube-dl. It's still going strong as ever, and fortunately for us Mac users, Adam Albrec's GUI frontend for youtube-dl, PPC Media Center, has also just been updated to version 5.0. The new version can stream or save to disk as always, but now also has an MP3 converter so you can save videos as MP3s.
On the Linux side, I'm still using youtube-dl in combination with my trusty script:
mpv --framedrop=vo --cache 8192 --cache-initial 410 $(youtube-dl -gf 18 $(xsel --clipboard))
This requires you have mpv and xsel installed in addition to youtube-dl. I've also been meaning to look at youtube-dlG, a graphical frontend for youtube-dl similar to PPC Media Center, only for Linux.
And if you can believe it, Youtube on Mac OS 9 isn't dead yet as YTBfC has been updated to work in the brave new world.
In a couple of other software updates to note, Adam Albrec's PowerPC Security Mode has been updated to address some Finder lock-up problems, and leopard-webkit recently released a slew of important security fixes.
PowerPC still has a pulse.