Well, it does start… anyway, it does if I delete the database and re-run the test app 
I’m not sure what you mean by “debug-level lopgging in CB Lite” - is that a flag ? I tried to locate it but couldn’t find it on the Db or Repl. configs?
I can see that the replication is starting. This is the output from the app (my “prints” and some thread info that is only showing when it is replicating:
2018-10-10 10:34:28.778665+0200 cb2.iOS[87618:14131135] Instantiate cb2.Services.DbDataStore
10:34:28.856492| [Couchbase]: (Startup) [1] CouchbaseLite/2.1.0 (.NET; iOS 12.0.0; iPhone) Build/232 LiteCore/2.1.0 (1275) Commit/26b467a
2018-10-10 10:34:28.865247+0200 cb2.iOS[87618:14131135] Database 'fangst' created
2018-10-10 10:34:28.876286+0200 cb2.iOS[87618:14131135] Log in with user: anonymous
2018-10-10 10:34:28.880699+0200 cb2.iOS[87618:14131135] Try to start the replicator...
Thread started: #2
Thread started: #3
2018-10-10 10:34:28.907423+0200 cb2.iOS[87618:14131135] repl. channels:
Thread started: #4
2018-10-10 10:34:28.912058+0200 cb2.iOS[87618:14131135] New database: -
2018-10-10 10:34:28.913923+0200 cb2.iOS[87618:14132322] Replication: Connecting to Sync.Gateway
2018-10-10 10:34:28.914387+0200 cb2.iOS[87618:14132322] Replication status: Couchbase.Lite.Sync.ReplicatorProgress - activity: Connecting. Completed: 0 of 0
Thread finished: #3
Thread started: #5
Thread started: <Thread Pool> #6
Thread started: <Thread Pool> #7
Thread started: <Thread Pool> #8
Thread started: <Thread Pool> #9
Thread started: <Thread Pool> #10
Thread finished: #4
Thread started: <Thread Pool> #11
Thread started: <Thread Pool> #12
Thread started: <Thread Pool> #13
Thread started: #14
Thread finished: #14
Thread started: #15
Thread finished: #15
Thread started: #16
Thread finished: #16
Thread started: #17
Thread started: #18
2018-10-10 10:34:29.018868+0200 cb2.iOS[87618:14132340] Replication: Busy transferring data
2018-10-10 10:34:29.019048+0200 cb2.iOS[87618:14132340] Replication status: Couchbase.Lite.Sync.ReplicatorProgress - activity: Busy. Completed: 0 of 0
Thread finished: #18
Thread started: #19
Thread started: <Thread Pool> #20
Thread started: <Thread Pool> #21