Yes! Spaces was designed to be compatible with S3 in order to take advantage of existing integration just like this. In order to mount a Space for external storage, you first need to enable the External Storage Support plugin just as you would for S3.
Next, add a new mount from the External Storages menu in the Admin panel. In the Bucket field, add the name of your Space. In the Host field, enter nyc3.digitaloceanspaces.com. In the Region field, use nyc3. You can fine the needed Access Key and Secret Key for your Spaces account on the Applications & API page of the DigitalOcean control panel. Finally, make sure to select Enable SSL. When successfully configured, a green dot should appear:
Additionally, you might want to enable sharing. This can be done the the Advanced Settings which can be accessed by click the "cog" icon on the right:
