You could use Package Browser (pkgbrowser). See screenshot. Set filter and other options as shown. It has a 'Repository' column. Click on it to sort. It shows I have 1 AUR package installed.
Type: Posts; User: Dennis N; Keyword(s):
You could use Package Browser (pkgbrowser). See screenshot. Set filter and other options as shown. It has a 'Repository' column. Click on it to sort. It shows I have 1 AUR package installed.