是否可以下载快照并将其安装在其他无法访问 Internet 的计算机上？

离线系统需要 snapd（snap 命令）。
离线系统需要 snap 设备。
离线系统不需要快照存储。

来自https://forum.snapcraft.io/t/offline-snap-installers-and-possibility-to-update/275：

$ snap download hello-world
Fetching snap "hello-world"
Fetching assertions for "hello-world"
kyrofa@Pandora:~$ sudo snap ack hello-world_27.assert 
kyrofa@Pandora:~$ sudo snap install hello-world_27.snap
hello-world 6.3 from 'canonical' installed
kyrofa@Pandora:~$ snap list
Name                   Version                   Rev   Developer      Notes
<snip>
hello-world            6.3                       27    canonical      -

离线快照的关键是您必须手动操作 snapd 数据库以告知它有关包和更新的信息。这就是“快照确认”命令。

示例中的以下 ack 表示：嘿，数据库，我当前的工作目录中存在一个名为 hello-world27.snap 的本地包。如果下载的包在其他地方，请添加完整路径。

 $ sudo snap ack hello-world_27.assert 

snapd 的手册页解释了更多关于 ack 的信息：

ack
   Add an assertion to the system

   The ack command tries to add an assertion to the system assertion data‐
   base.

   The assertion may also be a newer revision of a pre-existing  assertion
   that it will replace.

   To  succeed  the assertion must be valid, its signature verified with a
   known public key and the assertion consistent with and its prerequisite
   in the database.