Sounds like definitely Intel. Macs have EFI (Extensible Firmware Interface) rather than BIOS. Attach the install media and hold Option when powering up. This will take you to the EFI boot loader, where you should see icons for each potential startup disk. Select the Linux installer and hit Return or click the button to advance.
I don’t know which distros have the best support for different generations of Apple hardware. You should be able to get some sense of whether the distro is a good candidate from observing whether the mouse and kbd are functional before you commit to the install.