Borussia Mönchengladbach have entered the race alongside Celtic and Feyenoord...

https://tango-wiki.win/index.php/Is_a_%E2%82%AC5m_Clause_Something_Celtic_Can_Afford_Easily%3F

Borussia Mönchengladbach have entered the race alongside Celtic and Feyenoord for Hertha BSC goalkeeper Tjark Ernst. According to Bild, Ernst can be signed for a €5 million release clause