From what I understood, when I looked into it a while ago, some car makers use an encrypted ODB2 (needed by Comma.ai to communicate driving instructions).
See for example: https://autel.us/security-gateways/, 'Automakers with security gateways installed include Stellantis (Dodge, Chrysler, Ram, Alfa Romeo, FIAT, and Maserati), Nissan and Infinity, Mercedes-Benz, and Volkswagen and Audi.'
None of those busses are encrypted (at least not the majority I am familiar with). The security gateway is just a firewall.
Toyota TSS3 is in fact encrypted; openpilot users who have TSS3 have to manually extract decryption keys from their cars to be able to talk on the CAN bus.