Modern inkjets will not support Postscript or PCL at all. The only way around it is using something like a RPi or VM running netatalk + CUPS/Ghostscript to "create" a Postscript printer queue on the network that classic Macs can see. The printer server will convert the Postscript to whatever the printer wants. The Mac itself would need to have Ethernet or a Localtalk bridge.
Dark Castle was written in straight 68000 assembly language, taking advantage of very low-level processor instructions. I could see it being very easy to make it fail if certain functions were changed/implemented differently via an accelerator.
Just thought about this the other day. I know it's possible (with some limitations) to use an Imagewriter II on modern versions of macOS or Windows with a USB to Serial adapter.
I wonder if the opposite works... I have just bought a new Inkjet printer, it's a Canon TS8150. I use it over Wifi but it does have a USB B socket at the back.
I'm not too big a fan of old printers. I think they just require too much maintenance to get them properly working. My original IW's mechanism is completely stuck due to rust. The foam is also completely gone.
Hardware wise, this adapter would need to have the exact same wiring as the 'IW2 to USB' cable. I'm more worried about the software side of things. I found this Apple Communities thread about someone wanting to use a modern Brother laser printer with OS9. Someone recommended the OP to use the Laserwriter 8 drivers as they support PCL6. However, I have no idea if the Canon still supports this protocol?
Looking forward to your thoughts on this.