Brighton are aware of the interest and fielded an approach from PSV earlier this season, quoting a fee of €10m to sell. Such a price is deemed too steep by the Dutch giants.
Propper's contract with Brighton runs to 2023.
Partly due to injuries, Propper only played eleven games this season and was on the bench for the last six Premier League matches without playing minutes.
However, the Seagulls remain reluctant sellers at this time.