Yes, the OS is ROM based, on the chip under the space bar. The CF card is just an optional data partition.
For hardware "anything" is generally a stretch when it comes to CE. Your best best is to match something up that is on the HCL with the ebay links in the HCL:
https://www.hpcfactor.com/hcl/
For any compatible non-NE2000 cards, we usually have the drivers in the HCL.
Any updates can be found via H/PC:Update in the support section.
Power wise, you just need a generic universal DC adapter. . Just ensure that the polarity is correct for the device
(positive on centre if I recall
) and that it is adjustable to 5v. Don't leave it set to 12v and wind up pumping 12v down to it! Alternately just run it from AA's.
As for apps, you can find them in the SCL:
https://www.hpcfactor.com/scl/
I'll leave it to others to offer some app ideas.