digiKam is an Open-Source project Photos management software, specially for KDE but you can use it on Ubuntu or others distros too. In digiKam photos are organized in albums which can be sorted chronologically, by folder layout or by custom collections. Developers recently released digiKam 4.9.0 with 33 bug fixes. Developers main focus is on digiKam 5.0 release, as it is supposed to be a major release of digiKam.