After installing npm @openzeppelin/contracts@4.8.3, the contracts/token/ERC20/extensions folder only contains the file draft-ERC20Permit.sol (that should be deprecated as of 4.8.0) and does not have ERC20Permit.sol yet.
ERC Permit wasn't made official yet in the 4.8.3 release hence the draft prefix, it should be in the 4.9 release but is currently only in rc1 (and master)