Between 2011 and 2019, he was a soloist at the Deutsche Oper am Rhein in Düsseldorf. His repertoire includes more than 50 operatic roles, including Bartolo (Mozart’s Le nozze di Figaro), Masetto (Mozart’s Don Giovanni), Crespel (Offenbach’s The Tales of Hoffmann), Rocco (Beethoven’s Fidelio), Sparafucile (Verdi's Rigoletto), Banco (Verdi's Macbeth), Fafner (Wagner's Das Rheingold) and Hunding (Wagner's Die Walküre), as well as Minotaurus (Martinů's Ariadne). He also regularly performs a concert repertoire. He won the special prize in the International Song Festival in Istanbul in 2010.

Łukasz Konieczny had a significant success as Polifem in the stage première of Händel's Acis and Galatea during the International Händel Festival in Halle in 2013. Other important events in his career includes singing the bass part in Stravinsky's Les Noces during the 2013 Klavier Festival Ruhr, and the bass part in Krzysztof Penderecki's Polish Requiem during the Polish Music Festival in Krakow (2014). In 2015 the singer made his debut as Rocc in Beethoven's Fidelio at the Mainfranken Theater in Würzburg.

In Poland, he performed, among others, in the role of Doctor Behrens in the first performance of Paweł Mykietyn's Magic Mountain directed by Andrzej Chyra, commissioned by the 2015 Malta Festival in Poznań. The opera was also shown during the Sacrum Profanum Festival in Krakow and at the Warsaw Autumn Festival.

In 2017, Łukasz Konieczny made his debut on the stage of Bayerische Staatsoper in Munich as Barone Douphol in Verdi's La Traviata, alongside Plácido Domingo and Diana Damrau. He also performed as Sparafucile at Verdi's Rigoletto in Hamburg Staatsoper. In Théâtre du Capitole in Toulouse, he sang Mozart's Requiem. In the 2017/18 season he performed in Dresden Semperoper, where he played the roles of Crespel (The Tales of Hoffmann) and Lodovico (Verdi's Othello). In this season, Konieczny took part in a guest performance of the National Opera in Dubai, where he played the role of Pharaoh in Verdi's Aida.