I downloaded it on my Poco F7 Ultra via F-droid. Then I went on to phone's settings to set it as a Default Camera App. But it didn't appear there. The only app there was the phone's builtin currently default app.
Unfortunately Android doesn't have a concept of default camera app - it's no longer possible for apps to call third party camera apps, and behaviour such as launching from a gesture is device/company specific.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Unfortunately Android doesn't have a concept of default camera app - it's no longer possible for apps to call third party camera apps, and behaviour such as launching from a gesture is device/company specific.