Hey all,

Figured it out just minutes after posting via a bit more experimentation and comparison to SQL Developer! It turns out the "Connection Details" listed in SQL Developer spell out the full connection name. In my case, the successful SQL Developer connection details listed:

jkaufman@//localhost:1521/ORAPDB.oracledb.bell.local

I didn't need the username in front since the connection string already contains UID (in fact, leaving it there resulted in not connecting). But putting the host name and port in front must tell the connection how to succeed via straight TCP, no listener required. In full, this connection string works, and no longer prompts -- you just get the connection handle back as you would expect when issued with SQLSTRINGCONNECT():

DRIVER={Oracle in instantclient_12_2};
DBQ=localhost:1521/ORAPDB.oracledb.bell.local;
UID=jkaufman;
PWD=<password>;
HOST=localhost;
PORT=1521;
DefaultIsolationLevel=READUNCOMMITTED

Hope this is helpful to other folks! Oracle on Docker works out well, and did away with a day and a half of headaches I had when trying to install Oracle directly on Windows. And now I can access Oracle from VFP, too. I am sure performance is awful, but it's a start. Incidentally, Oracle also installed flawlessly on Docker for macOS. An example of getting Oracle 12c running on Docker can be found here -- this link helped me a TON:

https://www.dontesta.it/en/2019/08/26/how-to-setup-docker-container-oracle-database-12c-for-liferay-development-environment/

Thanks!
Joe Kaufman