The article author claims the networking software wasn't installed, though.
> Also SCSI tends to be easy to convert if one knows the drive connector/type, and is willing to chain a couple adapters.
I was thinking this too. And the author also says they didn't believe they'd be able to read the HFS volume, but Linux has had an HFS driver for... decades?... at this point.
In this case, it's a PowerBook Duo with a SCSI disk, so you'd need a Duo Dock or similar[2], a HDI-30-to-something-a-little-more-standard adapter [3], and whatever combination of cables, converters, and controllers are required to connect a parallel SCSI device into a more modern system.
For example, if you have a machine with a PCI Express slot (or Thunderbolt PCI Express enclosure), I'd recommend any of the LSI Logic Ultra320 adapters available on eBay for < $50, as drivers are readily available for macOS (AppleLSIFusionMPT.kext, included in all Mac OS versions worth mentioning, up to and including Sonoma, Intel and Apple Silicon), Linux (in-kernel mptspi driver), and Windows (the Windows Server 2008 driver[4] should work on current Windows versions).
Assuming all these things are in order, connect the Macs with a SCSI cable, hold down T while booting the PowerBook to enter target disk mode, and answer no to any prompts your OS may display offering to format the unreadable disk you just attached!
As for accessing the HFS filesystem, assuming macOS, my preferred method would be:
1. Create a raw disk image:
$ hdiutil create -tgtimagekey diskimage-class=CRawDiskImage -srcdevice disk<Number> <Name>.img
2. Shut down the PowerBook.
3. Make a backup copy of the image in case something goes wrong.
4. Install Mac OS 9 in qemu[5] and attach the image.
5. Use Alsoft PlusMaker[6] in Mac OS 9 to do an in-place conversion of the filesystem on the image from HFS to HFS+ (download the first file, use StuffIt[7] to extract the file and Toast[8] to mount the image, and run PlusMaker directly from the image to avoid being prompted for a serial number).
6. Shut down Mac OS 9 ("Shut Down" is in the Mac OS 9 Finder's "Special" menu).
7. Mount the resulting HFS+ image in (current) macOS (double-click in Finder, "hdiutil attach <Name>.img" from a command prompt, etc.).
Other options exist, but this is the easiest full-fidelity one that comes to mind.
As a bonus, you'll now have an emulated Mac OS 9 system that should run most of the applications from the original PowerBook's hard drive on your modern Mac.
[1] https://developer.apple.com/library/archive/technotes/tn/tn1...
[2] https://en.wikipedia.org/wiki/PowerBook_Duo#Docking_stations
[3] https://www.amazon.com/dp/B0081SAIS2/
[4] https://www.broadcom.com/support/download-search?pg=Legacy+P...
[5] https://wiki.qemu.org/Documentation/GuestOperatingSystems/Ma...
[6] https://www.macintoshrepository.org/19-plusoptimizer-plusmak...
[7] https://www.macintoshrepository.org/809-stuffit-deluxe-1-5-x...
[8] https://www.macintoshrepository.org/1724-toast-5-titanium
Also SCSI tends to be easy to convert if one knows the drive connector/type, and is willing to chain a couple adapters. I'm sure that is the case here too, the 2.5" scsi drives were a form of SCA connectors IIRC, SCSI adapters exist for almost anything to anything as long as the single ended vs differential rules are followed, newer ultra differential adapters could usually fall back to 8 bit single ended allowing them to drive just about everything. The problem is going to be finding an OS/etc that can real the old mac filesystems although I'm guessing one of the utilities to read raw images (of which i'm failing to remember the ones Ive used in the past) could probably read/write the raw disk image.