Nice day I'm testing the new version of elementary and I have a hard time in the application center. Applications available do not appear in repositories. I attach a screenshot
This question was answered in this post: Almost no apps on appcenter
If you sideload a flatpak from flathub.org you'll automatically add their repo, and populate Appcenter a bit more.
Other than that it seems AppCenter won't support deb packages anymore. So yes, you can still install deb programs via the terminal, but I'm afraid you'll then need to manually update them, because appcenter won't do it for you.
The reasoning for this apparently is that some users found non curated apps "ugly" so now they castrated the whole os for it.
Note: You will not immediately see the applications in AppCenter. In my case after installing an app from https://flathub.org/ it took a few reboots for finally show up all apps available. Unfortunately, you will only see Flatpak apps in AppCenter. to install apps from repositories, you will have to use terminal or download Eddy or other application to install .deb
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