We do not support multistream for streaming backups yet. A CCR will help to consider it on priority.
WE support multiple stream for backups with snap and block level in v11 .
For block level:
Till sp15: indexing v1 type is only supported which supports multiple stream for backup but not for restore.
With sp15: Indexing v2 is also supported. This supports multistream backup and restore.
On ubuntu, they have an option to run driverless block level backup.
With driverless they can take full backups and restores. Incremental, synth full backup and table level restore is not supported.
What is the kernel version and exact ubuntu version?
If File system iDA supports we can check for the support.
Ad you mentioned its non lvm volume. What is the configuration? Is it coming from a supported array? We support backup for local device also provided free extents are available