Ubuntu 22.04安装MonoDevelop时遭遇GPG密钥错误的解决求助

各位大佬，我在Ubuntu 22.04上安装MonoDevelop的时候碰到了棘手的GPG密钥问题，试了好几种方法都没解决，想请教下有没有可行的解决思路？

我先是跟着官方下载指南和一些Ubuntu教程的步骤操作，结果发现sudo apt-key ...命令直接报错说已经被弃用了。现在因为缺少对应的公钥，sudo apt update根本没法正常访问Mono的软件仓库，导致MonoDevelop完全装不了。

执行apt update时的错误输出如下：

Err:1 https://download.mono-project.com/repo/ubuntu vs-bionic InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A6A19B38D3D831EF
Reading package lists... Done
W: GPG error: https://download.mono-project.com/repo/ubuntu vs-bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A6A19B38D3D831EF
E: The repository 'https://download.mono-project.com/repo/ubuntu vs-bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

我也尝试过用gpg相关命令手动导入密钥，但不管试哪一种，apt update还是会报缺少密钥的错误。我试过的命令包括：

• 通过Ubuntu密钥服务器导入完整密钥：
  curl -sSL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF" | gpg --import
• 只导入报错的目标密钥：
  curl -sSL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0xA6A19B38D3D831EF" | gpg --import
• 从Mono官方仓库导入gpg文件：
  curl -sSL https://download.mono-project.com/repo/xamarin.gpg | gpg --import
• 直接从Mono的密钥服务器接收密钥：
  sudo gpg --keyserver download.mono-project.com --recv-key 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

另外我也考虑过用Snap来安装，但翻遍了Snap商店都找不到MonoDevelop的包。有没有人知道怎么在Ubuntu 22.04上成功搞定MonoDevelop的安装啊？

备注：内容来源于stack exchange，提问作者nobody