All:
I had originally posted this question last weekend, and several people responded with the answer.
And I wanted to thank them,.
However, I accidentally deleted the original post while trying to move it, so here is for the great brain-trust in the cloud:
For reasons passing understanding:
L2TP VPN Protocol is not supported when an ASA5500-X is in multi-context mode
Per: https://www.cisco.com/c/en/us/td/docs/security/asa/asa97/configuration/vpn/asa-97-vpn-config/vpn-l2tp-ipsec.html
FWCLUSTER6/context0(config)# group-policy DfltGrpPolicy attributes
FWCLUSTER6/context0(config-group-policy)# vpn-tunnel-protocol ?
group-policy mode commands/options:
ikev1 IKE version 1
ikev2 IKE version 2
l2tp-ipsec L2TP using IPSec for security <--- MISSING in Context Mode
ssl-client SSL VPN Client
ssl-clientless SSL Clientless VPN <--- MISSING in Context Mode