Can anyone suggest a scanner, with software included, that works well with the iMac (OS 10.13.6).

Check which of the 6600+ scanners is already supported by the paid, non-subscription, 64-bit VueScan where it states that it does not require vendor scanning software, or drivers to support the scanner. That way, when the vendor inevitably drops support for your scanner, you won't care.

Another vote for VueScan.

You are welcome.