Sending from the offline wallet still prompts error: There are no funds. I am BTC is on the BTC network and the offline wallet is only to use the private key to sign the standard watching only wallet's transaction,
Don't use the offline Electrum to send.
I see that no one provided you any instructions, these are the correct steps on how to do it in offline Electrum and watch-only Electrum pair:
https://bitcoinelectrum.com/creating-a-cold-storage-wallet-in-electrum/For non-Electrum watch-only wallet, read my previous reply.
-snip-, however I am still trying to sort out restoring the wallets first.
Yes, better stick to the original topic issue, this thread has deviated from it since you've brought up discussion about Cold Storage and Tails.
You may create a new topic if you have additional questions or if want to continue those discussions.
Honestly, I was in the impression that you've already figured it out after that post and the subsequent replies below it.
So I've been restoring the old Trezor 24 word mnemonic/seed phrase multiple times with its passphrase.
A new Electrum BIP39 wallet is created with nothing, probably as there's no funds or transactions on the old Trezor cold wallet.
I'm using the correct mnemonic/seed 24 words and passphrase.
It seems as the Trezor had 0 funds, this may not have created any history or addresses.