The FTA channels I'm aware of require a satellite to receive, receiving them any other way would mean using apps that have various tv channels as an option.
While most are, through out the republic, only available on 'FreeSat' we also have terrestrial namely 'Saorview'. Both will need a tuner added to the PC to receive them.
Depending on location you may be, using an aerial, able to receive the Uk terrestrial bouquet of 'Freeview' along with 'Saorview', otherwise a satellite dish will be required to receive 'Freesat'.