Which wallet are you using? I have not seen 0 sat/vbyte before when making transaction, it starts from 1 sat/vbyte.
You can download Electrum wallet from their official site, create address and start using their wallets to make transactions you can perform transactions with the least of 0-1 sat/vbyte.
You can not use SPV wallets (like Electrum) to make 0 sat/vbyte transaction. Even if possible you are able to customize it to 0 sat/vbyte, nodes will reject it and you will not be able to broadcast the transaction.
If you want to send with 0 sat/vbyte, you will need to run your own node. But no miner (mining pool) will accept the transaction which will still makes it later drop from mempool. But if you know a miner that can help you include the transaction into a block, it will work.
Is it possible to adjust the fee rate to 0 sat/vbyte on Electrum wallet?
It is not possible.
Even if it is, I wouldn't advise you to do it because miners prioritize transactions with higher fee rates. Sending a transaction with 0 sat/vbyte means it will be overlooked by the miners. It will be the last in the queue among unconfirmed transactions, and it might even be stuck indefinitely in the mempool.
Exactly.
That's true, the fee is adjustable on electrum and that is provided you're making use of a desktop to perform this, whereby it provides you the privilege of inserting the amount you wanted to be charged as fee, than the one it suggest and bring to you, though it may not be zero completely in this regards, but some like this for instance 0.5, 0.6 or even 0.3 sat/vbyte respectively.
It can not go below 1 sat/vbyte on Electrum.
Thanks @Charles-Tim for the clarification on this, i actually thought i cold be some thing below 1 sat/vbyte as @SmartGold01 already pointed out, but the beauty of it is that, even if the wallet we use allow for the customization, the nodes will have to reject any fee below 1sat/vbyte.
Over the years, I've been used to this common rate of 1sat/vbyte even before the introduction or ordinance clogging the block space, you can easily see transaction fees at this said rate until thing begin to change and everything got out of hands with transaction fees.