Are there any good exchanges that offer access via Tor ?
You will not increase security/privacy when using Tor/.onion as much as you are more likely to be scammed.
All platforms that require proof of identity (KYC/AL) will not use Darknet URLs.
You can try some alternatives such as:
Be careful, if you do not want to be exposed to risk, it is best to use this forum and exchange with trusted people.