How do I resolve 'Please upgrade your Plug-ins' error in InDesign on PowerBook G4?

What's missing is the specific version of Creative Suite you're running, although it might be moot... the last version of Creative Suite was released in 2012 - 13 years ago, and everything was migrated to Creative Cloud.

Given that you're running MacOS 10.4 - software that was released 20 years ago, I'm leaning towards your system being too out of date for any updates. Adobe almost certainly don't maintain any update servers (which is likely where you'd get any plugins from) for this old a version, and neither do Apple.

As for Safari, it's suffering from the same aging problem - the web has moved on from what it was 20 years ago especially in the security realm. Specifically, such an old version of Safari wouldn't support the newer security/encryption standards, and many sites won't let you connect with insecure connections, hence Safari isn't able to get there.

Unfortunately, maintaining and updating what is now considered a vintage system is hard, and will only get harder.

brrybrenner wrote:

Secondly, Safari version 4.1.3 (4533.19.4) can't establish a secure connection to the server.

That's no surprise. The original protocol used for https security was found to be less secure than thought, and there was a big push to upgrade Web sites and browsers to use a more secure protocol.

The changes to support the more secure protocol first went into El Captain (OS X 10.11.*).

They would not have been back-ported to Mac OS X 10.4, or any other version of Mac OS X that could run on a PowerPC-based Mac.

There was apparently a hobby project called TenFourFox. (Note that this was not an official Mozilla project.)

It was a fork of a really old version of Firefox (Firefox 45), with changes to keep the code compatible with Mac OS X 10.4 and the Power Macintosh. It might be able to negotiate modern https security. However, it is so old in so many ways, and lacking in enough features, that you still might have trouble accessing modern Web sites with it.

TenFourFox Development (March 29, 2021) – The end of TenFourFox and what I've learned from it

I'm guessing that it wouldn't be worth trying to get the last version up and running on that old PowerBook G4; that it's time to move on, even if your choices these days are between

• Paying "subscription" (rental) fees for Adobe products, or
• Switching to something else

But it is interesting that this project existed.

I still have PowerBook G4 running Mac OS X Leopard 10.5.8. I have a long time ago retired it for DV/D8 Firewire import and old iMovie 1.0.2-6.0.3 although I have two newer Macs that can still do that (and an old PowerMac 8600/200 with Firewire, ATA and CPU upgrade XLR8 cards -- it can run System 9.0.4 or older and optionally also Mac OS X 10.2.7 Jaguar via XPostFacto).

I tested TenFourFox for "surfing" the net long after retiring the PB G4. It worked but was quite slow and that app is no longer updated anyway.

About 15 years ago I installed some Linux version (at least AFAIR Mint) to that PB G4. It worked after some fiddling but did not feel any faster so I re-installed Leopard.