The former Swindon Town forward, 21, struggled to make an impact at Goodison Park and had loan spells at Plymouth Argyle, Huddersfield Town and Motherwell.
"We are delighted to have Lukas on board and this adds more strength to the squad," said the Coventry manager Aidy Boothroyd.
"We wanted to enhance our attacking options and this will certainly do that. He is at the right age too, to grow and develop with Coventry City."
Midfielder Darren Ambrose has signed a three-year contract extension with Crystal Palace.
He had been linked with Queens Park Rangers, and would almost certainly have been sold had a takeover of the club not gone through this summer.
"Its a been a hard few months with all the speculation about my future but I am now delighted to be sitting here signing the new contract," he told Palace's official website.
"I have always wanted to remain at this football club and I am pleased it is all resolved."
Nottingham Forest have had a bid for Sheffield Wednesday's Jermaine Johnson rejected.
Reports put the figure offered for the winger at around £350,000. Wednesday are £26million in debt and face a winding up order over an unpaid tax bill of £550,000.
Swansea City have offered a trial to AZ Alkmaar's Dutch midfielder Kemy Agustien.