JOSM is a visual editor for OpenStreetMap. The website of JOSM is https://josm.openstreetmap.de/
Installing JOSM from the Flathub repository
flatpak --user remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
flatpak --user install flathub org.openstreetmap.josm
Updating JOSM from the Flathub repository
flatpak --user update org.openstreetmap.josm
To run JOSM from command-line
flatpak run org.openstreetmap.josm