Convert and Manipulate Images With ‘Converter’ GUI Tool in Linux
Converter is an open-source graphical front-end that enables you to do that. It is a GTK4+libadwaita application.
You can convert the images to various file formats that include png, webp, jpeg, heif, heic, and bmp. It is safe to say that you get support for the most popular image file formats. So, it should come in pretty handy.