raspiBackup is supported with RaspbianOS and Raspberry hardware only. But raspiBackup can also be used successfully on different hardware with different Linux distributions. Just test raspiBackup on your environment and be happy if it works. But if it fails or you get error messages there is no support. Given the fact raspiBackup is maintained and supported for free
1) It's too expensive for me to buy all possible hardware required for tests
2) it's too expensive for me to setup and execute all test combinations
3) it's to expensive for me to execute all tests every time a new release will be published.
There exists a small script in github which tests whether the present environment is supported by raspiBackup. (see here)