I recently prepared a database report to show the frequencies that are used for 6M QSOs. In this report, the QSOs are only those logged by stations in Europe between 1 September 2018 and 31 August 2019 (hopefully, therefore, encapsulating pretty much a full 6M season).
By showing the QSO totals cumulatively, it’s easy to spot that the majority of QSOs are made on or around 50.313MHz, which is the centre of FT8 activity at the moment. I think it’s fair to say that this trend would also be apparent on every amateur band, right down to 160M. I hope to prepare a report showing if this is the case.