Old Laserwriters on High Sierra

Pursuing a LocalTalk solution is a dead end due to the utter lack of AppleTalk support. Read Snow Leopard means no more Appletalk - Apple Community.

All hope is not lost though. The following describes your options. I'll start with what little good news there is.

LaserWriter Select 360 and Pro 630: possible, by using their parallel port with a suitable print server or USB to parallel converter as described in this Discussion and the links within it: LSW Select 360 prints via Airport and Lion? | Official Apple ...

Read the "other old thread" I alluded to in that Discussion for even more details with links to extensive research. Matt Broughton was very helpful to me in the past but I think he's long since lost interest.

I used a D-Link wireless print server for my LW Select 360 until it finally expired due to a logic board failure plus my lack of motivation to fix whatever's wrong with it. I did not include a link to the print server I use because it was discontinued a long time ago, but the other products I described in that Discussion may still be available.

If you pursue that solution Apple's generic PostScript driver is all you need by way of software. No, it's not nearly as capable as model-specific drivers provided by HP, but they ceased being interested in Apple well over a decade ago.

Finally the bad news: Using a Personal LaserWriter 320 is not possible without a LocalTalk-capable Mac. The printer sharing idea is the only way because that printer lacks anything other than a LocalTalk port... and LocalTalk requires AppleTalk... hence the dead end.

I wonder if PPDs from Tiger could be put into the HS Library.

Sadly no. It's a lot more complicated than that. CUPS really isn't going to help much either, but for a very abbreviated description of what it's good for read Apple ImageWriter printer installation in OS X (tl;dr you really can't do much more with CUPS than what it already provides in System Preferences > Printers & Scanners).

Kudos to John Galt's excellent reply.

With regards to AppleTalk only printers - a possible solution would be to run either a Linux or Mac virtual machine. The Mac virtual machine would need to be a much older version of the Mac operating system i.e. one which still supported AppleTalk. I suspect in this case rather than the more usual NAT or routed network config for the VM you would need to use a bridged mode so the VM can directly access the network, it should then in theory be able to see the AppleTalk traffic from the Farallon or Asanté bridge. It might then be possible for the VM in turn to 're-share' the printer over TCP/IP so that the host Mac can also access it. Even if this is not possible in a Mac specific manner you might be able to share it using Windows networking which the parent Mac can use to access the printer queue.

Arguably going this far is getting silly and it might be time to consider a new printer, apart from anything else getting consumables i.e. ink/toner is going to be hard for such old printers. Newer models are also faster and use less electricity.

With regards to using a Linux VM you can still install Netatalk in to Linux which adds AppleTalk support. See - https://help.ubuntu.com/community/AppleTalk#AppleTalk_Printing

Once the Linux VM is itself able to access the printer it can re-share it to the parent Mac.