Tried that on Coinomi, is it possible I'll find them differently with Electrum or BlueWallet?
As far as I know, Coinomi generates the legacy wallet on the derivation path of m/44'/0'/0' as well.
If you don't see your balance on Coinomi, maybe xpub you used for creating the watch-only wallet has been dervied on a different derivation path.
Didn't you create multiple wallets on Trezor? If I am not wrong it generates the second wallet on derivation path of m/44'/0'/1', the third wallet on m/44'/0'/2' and so on.