I uninstalled the old FPC and old Lazarus, then installed new FPC from debian packages, then installed all the 0.9.30 lcl packages as well as 0.9.30 lazarus-doc and lazarus-src packages successfully.
When I tried to install lazarus-ide-gtk2-0.9.30, Gdebi said it depends on lazarus-ide-0.9.30. When I tried to install lazarus-ide-0.9.30, it said it depends on lazarus-ide-gtk-0.9.30. But lazarus-ide-gtk-0.9.30 is not in the download.