I still don't have the full answer, but I found steps at https://support.ledger.com/hc/en-us/articles/6275459128989-How-to-analyze-a-Bitcoin-BTC-account-xPub?docs=true to be a helpful start:

1. go to Ledger Live > Accounts > Bitcoin > wrench icon > Advanced and grab my "xpub" string
2. Use https://www.blockonomics.co/views/segwit_xpub_convert.html to convert it to a zpub string
3. Use https://blockpath.com/ or https://www.cointracker.io/wallet/bitcoin?address=xxxxxx to view the total balance.

See also https://support.cointracker.io/hc/en-us/articles/4413049732625-What-is-xPub-yPub-zPub-and-UTXO-

I still have not found an API that can return the BTC total balance from a zpub address.

I still don't have the full answer, and the following is only for BTC (I'd prefer an answer that works across many blockchains):

I found steps at https://support.ledger.com/hc/en-us/articles/6275459128989-How-to-analyze-a-Bitcoin-BTC-account-xPub?docs=true to be a helpful start:

1. go to Ledger Live > Accounts > Bitcoin > wrench icon > Advanced and grab my "xpub" string
2. Use https://www.blockonomics.co/views/segwit_xpub_convert.html to convert it to a zpub string
3. Use https://blockpath.com/ or https://www.cointracker.io/wallet/bitcoin?address=xxxxxx to view the total balance.

See also https://support.cointracker.io/hc/en-us/articles/4413049732625-What-is-xPub-yPub-zPub-and-UTXO-

I still have not found an API that can return the BTC total balance from a zpub address.