I tried both of these solutions and neither worked. However, I did solve the problem through some random guess and check.
Turns out that a Cisco VPN installed on the machines was interfering with Kerberos authentication. I don’t know why this was happening, although I would guess that the VPN either installed Encryption capabilities that Spark can’t handle (evidenced by the Unsupported encryption type (14) error message) or that the VPN hijacked part of the encryption subsystem. I’m leaning toward the first.
Either way… it’s working!!!
Thank you kindly for your support in troubleshooting this!
NonSec.