… for SailfishOS ≥ 4.6 (only!).
P.S. / Edit:
Yes, now you do not have to (and should not) configure anything specifically any longer when using SailfishOS 4.6 or 5.0.
But this issue (i.e. “no specific Chum repository for this SailfishOS release yet available”) will be recurring with every new, major SailfishOS release (i.e. next: 5.1), as well documented at many places (RTFM).
Ultimately I just wanted to clearly state: Do input a version number with four fields (separated by full stop characters) for SailfishOS < 4.6. and a two fields one for ≥ 4.6, when you have to manually set the SailfishOS version number in the SailfishOS:Chum GUI app.