Digikam is a very powerful and complex software to manage photos. I was using shotwell previously for quite some time, but it's capabilities are limited. Wherever you go, digiKam is recommended instead.
The best things in digiKam so far are hierarchical tags and automatic face detection. But on the other hand: why is it not possible to simply export the images and remove metadata or resize during that process? You even have to use the 'external Storage exporter'-Plugin, which is not included in digiKam, but lives in the kipi-Plugins.
If you use oldstyle harddrives to store your photos make sure to save the digiKam database on some fast SSD storage. The performance improvements are worth it.
In the first version of this post I had some trouble with digiKam crashes, but I haven't encountered any in the last years.