Tethering software for Mac OS 10.14

CaptureOne Pro can do tethering. Once you have a license you can install earlier versions including C1 version 21 (14.4.1) which was the last version compatible with Mojave. (It's now up to version 23). Note that C1 is available as either perpetual license or subscription - if you prefer the subscription you will need to confirm with PhaseOne if you can install an old version under the subscription program.

"Tethering" has a number of connotations but I'm not sure if any of them would be applicable in your circumstances.

If Adobe needs a later macOS version I suppose you will need to update macOS. If your Mac can't be updated past Mojave then I'd research alternatives to Lightroom. I realize Adobe is the product leader in its class but you have to be willing to put up with its business model of forcing you to pay for upgrades, one way or another.

Understandable. If you don't mind I will ask the site Hosts to relocate your question to the Earlier Operating Systems Community since it's not specific to the more limited MacBook Community. Hopefully it will get more visibility there, but if you don't get any more useful suggestions just create a brand new Discussion.

Questions with no replies tend to elicit more interest. Since I now understand what you're looking for I'll just keep quiet about it.