在从Ubuntu提要安装了.NET 6 SDK之后，我按照这里的说明安装了.NET 7 SDK。

wget https://packages.microsoft.com/config/ubuntu/22.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
sudo dpkg -i packages-microsoft-prod.deb
rm packages-microsoft-prod.deb

sudo apt-get update && sudo apt-get install dotnet-sdk-7.0导致此错误：

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package dotnet-sdk-7.0 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'dotnet-sdk-7.0' has no installation candidate

sudo apt show dotnet-sdk-7.0 -a的结果如下：

Package: dotnet-sdk-7.0
Version: 7.0.102-1
Priority: standard
Section: devel
Maintainer: Microsoft <dotnetcore@microsoft.com>
Installed-Size: 358 MB
Depends: aspnetcore-targeting-pack-7.0 (>= 7.0.2), netstandard-targeting-pack-2.1 (>= 2.1.0), dotnet-apphost-pack-7.0 (>= 7.0.2), dotnet-runtime-7.0 (>= 7.0.2), dotnet-targeting-pack-7.0 (>= 7.0.2), aspnetcore-runtime-7.0 (>= 7.0.2)
Homepage: https://github.com/dotnet/core
Download-Size: 90,6 MB
APT-Sources: https://packages.microsoft.com/ubuntu/22.04/prod jammy/main amd64 Packages
Description: Microsoft .NET SDK 7.0.102
 .NET is a development platform that you can use to build command-line applications, microservices and modern websites. It is open source, cross-platform and is supported by Microsoft. We hope you enjoy using it! If you do, please consider joining the active community of developers that are contributing to the project on GitHub (https://github.com/dotnet/core). We happily accept issues and PRs.

Package: dotnet-sdk-7.0
Version: 7.0.101-1
Priority: standard
Section: devel
Maintainer: Microsoft <dotnetcore@microsoft.com>
Installed-Size: 358 MB
Depends: aspnetcore-targeting-pack-7.0 (>= 7.0.1), netstandard-targeting-pack-2.1 (>= 2.1.0), dotnet-apphost-pack-7.0 (>= 7.0.1), dotnet-runtime-7.0 (>= 7.0.1), dotnet-targeting-pack-7.0 (>= 7.0.1), aspnetcore-runtime-7.0 (>= 7.0.1)
Homepage: https://github.com/dotnet/core
Download-Size: 90,6 MB
APT-Sources: https://packages.microsoft.com/ubuntu/22.04/prod jammy/main amd64 Packages
Description: Microsoft .NET SDK 7.0.101
 .NET is a development platform that you can use to build command-line applications, microservices and modern websites. It is open source, cross-platform and is supported by Microsoft. We hope you enjoy using it! If you do, please consider joining the active community of developers that are contributing to the project on GitHub (https://github.com/dotnet/core). We happily accept issues and PRs.

Package: dotnet-sdk-7.0
Version: 7.0.100-1
Priority: standard
Section: devel
Maintainer: Microsoft <dotnetcore@microsoft.com>
Installed-Size: 352 MB
Depends: aspnetcore-targeting-pack-7.0 (>= 7.0.0), netstandard-targeting-pack-2.1 (>= 2.1.0), dotnet-apphost-pack-7.0 (>= 7.0.0), dotnet-runtime-7.0 (>= 7.0.0), dotnet-targeting-pack-7.0 (>= 7.0.0), aspnetcore-runtime-7.0 (>= 7.0.0)
Homepage: https://github.com/dotnet/core
Download-Size: 88,4 MB
APT-Sources: https://packages.microsoft.com/ubuntu/22.04/prod jammy/main amd64 Packages
Description: Microsoft .NET SDK 7.0.100
 .NET is a development platform that you can use to build command-line applications, microservices and modern websites. It is open source, cross-platform and is supported by Microsoft. We hope you enjoy using it! If you do, please consider joining the active community of developers that are contributing to the project on GitHub (https://github.com/dotnet/core). We happily accept issues and PRs.

还尝试了apt-get upgrade
/etc/apt/sources.list.d/microsoft-prod.list包含以下内容：

deb [arch=amd64,arm64,armhf] https://packages.microsoft.com/ubuntu/22.04/prod jammy main