Just for curiosity, i finally got an answer from the seller. Indeed, i sent him a message some days ago, and forgot about it since i though i won't get any answer. I was wrong. Although i gave up the idea of buying from him, i'm puzzled regarding his answer: "We actually install Coinomi wallet onto the device as a default but the the USB can certainly work with electrum as well!"
What makes you puzzled? I think they mean you can install Electrum and store Electrum's data on USB device they sell. Although Coinomi have mixed reputation since in past,
1. Switched from open source to closed source wallet.
2. There was time interval where they doesn't upgrade their software and active in social media.
3. They send generated seed phrase to google server.
On side note, i just noticed that ebay mentioned 11 sold of those USB have been sold.
Do you mean that, according to the seller answer, the USB stick the seller sells *would work* as a ledger nano?