The official Crystal snap is available

During the Snapcraft Summit Crystal team released the official snap package of the Crystal language

On Ubuntu 16.04 or later, you can install the Crystal snap with the following command:

sudo snap install crystal --classic

Snap uses the "channel" feature to release multiple Crystal series concurrently. For example, without specifying a channel, currently Crystal 0.29.0 will be installed. But if you want to install 0.30.0-dev, specify the latest/edge channel as follows:

sudo snap install crystal --edge --classic