Adopt OpenJDK(GitHub) から入手します。

bionic64:~/src$ git clone https://github.com/AdoptOpenJDK/openjdk-jdk11u.git
Cloning into 'openjdk-jdk11u'...
remote: Enumerating objects: 880596, done.
remote: Counting objects: 100% (880596/880596), done.
remote: Compressing objects: 100% (113863/113863), done.
remote: Total 880596 (delta 713024), reused 880543 (delta 712973), pack-reused 0
Receiving objects: 100% (880596/880596), 1.95 GiB | 4.87 MiB/s, done.
Resolving deltas: 100% (713024/713024), done.
Checking out files: 100% (66186/66186), done.

OpenJDK 11 の最新タグを checkout します。

bionic64:~/src$ cd openjdk-jdk11u/
bionic64:~/src/openjdk-jdk11u$ git tag|grep jdk-11.0.1
jdk-11.0.1+0
jdk-11.0.1+1
jdk-11.0.1+10
jdk-11.0.1+11
jdk-11.0.1+12
jdk-11.0.1+13
jdk-11.0.1+2
jdk-11.0.1+3
jdk-11.0.1+4
jdk-11.0.1+5
jdk-11.0.1+6
jdk-11.0.1+7
jdk-11.0.1+8
jdk-11.0.1+9
bionic64:~/src/openjdk-jdk11u$ git checkout jdk-11.0.1+13 -b jdk-11.0.1+13
Switched to a new branch 'jdk-11.0.1+13'