A simple tool to fill out and annotate PDFs
Lossless Cut has saved me GigaBytes of storage by allowing me to trim videos losslessly. This is a must for video.
Run Android apps in Linux https://anbox.io/
Siril is an astronomical image processing tool, able to convert, pre-process images, help aligning them automatically or manually, stack them and enhance final images. https://www.siril.org/