Spotlight "Indexing and searching disabled" for external drive

I have one external drive that I store my iTunes library and other files on. I can NOT get spotlight to work on this drive. It is a 4 TB disk, formatted as "Mac OS Extended (Journaled)". In the terminal, if I try: mdutil -sa, I get the following (Calvin is the external drive):

mdutil -sa

/:

Indexing enabled.

/Volumes/Calvin:

Indexing and searching disabled.

I have tried the following (several times) WITHOUT success:

1. Resetting spotlight via System Preferences > Spotlight > Privacy by adding the external drive to the excluded list, saving the preferences, then removing the external drive from the excluded list and saving the preferences.

2. I have tried "Ignore ownership on this volume" on and off.

3. Via the CLI, turning off SIP, deleting the spotlight indexes, forcing re-indexing, turning SIP back on with the following commands:

boot with command-R

open terminal

csrutil disable

reboot

open terminal

sudo mdutil -i off /

sudo rm -rf /.Spotlight*

sudo mdutil -i on /

sudo mdutil -E /

boot with command-R

open terminal

csrutil enable

reboot

Does anyone have experience getting this fixed? Ideas? This is on 10.14.6, but was occurring in earlier versions of MacOS too.