Some days ago I wanted to connect a nikon camera with my Sailfish xperia 10 ii, I checked the links from dslrdashboard site and didn’t work for download. Hopefully I had the .apk from 7 years ago when it was available, I installed it and it worked quite well. I might have also some source code from when was available. If you duckduckgo-it ( qDslrDashboard apk ) you will find it (no ideas how reliable the sites are).
If you manage to install the app, the procedure is to activate the wifi on the camera, connect your device as to any wifi (camera name will appear on available wifis). After that run the app, and press NIKON / CANON / SONY (whatever camera you have). Interface is clean and easy to use. Some times it stuck, I clear cache and data from Settings-> Apps → qDslrDashboard.