If you're going to use an older Mac, you should still be able to install Ubuntu but you'll need to pay attention to how the boot process works for older hardware.
Ọ bụrụ na ị na-aga iji Mac meworo okenye, ị ka ga-enwe ike ịwụnye Ubuntu mana ị ga-achọ ịṅa ntị otú usoro buut si arụ ọrụ maka ngwaike okenye.