How does daml-on-fabric choose a channel on my fabric instance?

Just as the topic says, is it a default one? Is it configurable?

It is speciified in the config specified to daml-on-fabric,

so by default in config-local.yaml it is

digital-asset/daml-on-fabric/blob/10d8ef1d50587b40dc14318f4ddded2b189df2da/config-local.yaml#L88-L89

channel:
  name: mainchannel

channel:
  name: **mainchannel**
  channelTxFile: src/test/fixture/tmp/data/mainchannel.tx
  endorsementPolicy: src/test/fixture/tmp/data/endorsement-policy.yaml
  chaincode:
    name: daml_on_fabric
    type: golang
    version: 1.0
    gopath: chaincode
    metapath: chaincode/src/github.com/digital-asset/daml-on-fabric/META-INF
    entryPath: github.com/digital-asset/daml-on-fabric
    queryWaitTime: 30000
    invokeWaitTime: 60000