There's nothing new under the sun. This PowerBook G4 has two partitions, one for Leopard & one for Tiger. I found an already-working instance of TenFourFoxBox dating back to Jan 29, 2016, which I'd totally forgotten about. I've uninstalled TenFourFox & TenFourFoxBox from the Tiger partition, replacing them with aliases to the originals in the Leopard partition.
Thus far I have 104FoxBox working to access Cappuccino, Pnut (via Noodleapp), Mastodon, Counter.social & iCloud.