The real deadlock on process network initialization was found: the volume downloader did not write asynchronously, which would result it waiting on writing to a process that would never be created.

Duplicati/Library/Main/Operation/Restore/Channels.cs

@@ -9,10 +9,10 @@ namespace Duplicati.Library.Main.Operation.Restore
         // TODO Should maybe come from Options, or at least some global configuration file?
         private static readonly int bufferSize = 128;
 
+        public static readonly ChannelMarkerWrapper<Database.LocalRestoreDatabase.IFileToRestore> filesToRestore = new(new ChannelNameAttribute("filesToRestore", bufferSize));
         public static readonly ChannelMarkerWrapper<BlockRequest> downloadRequest = new(new ChannelNameAttribute("downloadRequest", bufferSize));
         public static readonly ChannelMarkerWrapper<(BlockRequest, IDownloadWaitHandle)> downloadedVolume = new(new ChannelNameAttribute("downloadResponse", bufferSize));
-        public static readonly ChannelMarkerWrapper<Database.LocalRestoreDatabase.IFileToRestore> filesToRestore = new(new ChannelNameAttribute("filesToRestore", bufferSize));
-        public static readonly ChannelMarkerWrapper<(BlockRequest, byte[])> decompressedVolumes = new(new ChannelNameAttribute("decompressedVolumes", bufferSize));
         public static readonly ChannelMarkerWrapper<(BlockRequest, TempFile)> decryptedVolume = new(new ChannelNameAttribute("decrytedVolume", bufferSize));
+        public static readonly ChannelMarkerWrapper<(BlockRequest, byte[])> decompressedVolumes = new(new ChannelNameAttribute("decompressedVolumes", bufferSize));
     }
 }

Duplicati/Library/Main/Operation/Restore/VolumeDownloader.cs

@@ -45,7 +45,7 @@ namespace Duplicati.Library.Main.Operation.Restore
                             }
                         }
 
-                        self.Output.Write((block_request, f));
+                        await self.Output.WriteAsync((block_request, f));
                     }
                 }
                 catch (RetiredException ex)

Duplicati/Library/Main/Operation/RestoreHandler.cs

@@ -151,8 +151,8 @@ namespace Duplicati.Library.Main.Operation
                     var filelister = Restore.FileLister.Run(db, backend, filter, m_options, m_result);
                     var fileprocessors = Enumerable.Range(0, file_processors).Select(i => Restore.FileProcessor.Run(db, fileprocessor_requests[i], fileprocessor_responses[i], m_result)).ToArray();
                     var blockmanager = Restore.BlockManager.Run(fileprocessor_requests, fileprocessor_responses);
-                    var volumedecrypters = Enumerable.Range(0, volume_decrypters).Select(i => Restore.VolumeDecrypter.Run()).ToArray();
                     var volumedownloaders = Enumerable.Range(0, volume_downloaders).Select(i => Restore.VolumeDownloader.Run(db, backend, m_options)).ToArray();
+                    var volumedecrypters = Enumerable.Range(0, volume_decrypters).Select(i => Restore.VolumeDecrypter.Run()).ToArray();
                     var volumedecompressors = Enumerable.Range(0, volume_decompressors).Select(i => Restore.VolumeDecompressor.Run(m_options)).ToArray();
 
                     all =