Thanks for these hints. I was able to fix all six errors in the configuration. The other four problems “Error loading inspector” are still existing. I will open another thread because I believe the problem about inspector editor is a different one and I mark this thread here as SOLVED.
Here a summary about the solution for all others who have got similar problems using Neos 2.3.8 at DomainFactory:
- After installation drop the Neos.Demo site and create a new one
./flow site:prune
./flow package:delete Neos.Demo
./flow kickstart:site MY.Seiten mysite.de
./flow site:import MY.Seiten
- Flush the cache, rebuild it
export FLOW_CONTEXT=Production
./flow flow:cache:flush --force
./flow flow:core:compile && ./flow doctrine:compileproxies && ./flow flow:cache:warmup
- After that you are able to log into backend and you will see 6 errors in the configuration:
Settings.TYPO3.Flow.resource.publishing -> This property is not allowed here, check the spelling if you think it belongs here.
Settings.TYPO3.Flow.resource.fileSystem -> This property is not allowed here, check the spelling if you think it belongs here.
Settings.TYPO3.Flow.resource.mirrorMode -> This property is not allowed here, check the spelling if you think it belongs here.
Settings.TYPO3.Flow.security.authentication.providers.Typo3SetupProvider.requestPatterns.controllerObjectName -> expected: type=dictionary, null found: type=string
Settings.TYPO3.Flow.security.authentication.providers.Typo3BackendProvider.requestPatterns.Flowpack\Neos\FrontendLogin\Security\NeosRequestPattern -> expected: type=dictionary, null found: type=string
Settings.TYPO3.Flow.security.authentication.providers.Flowpack.Neos.FrontendLogin:Frontend.requestPatterns.Flowpack\Neos\FrontendLogin\Security\NeosRequestPattern -> expected: type=dictionary, null found: type=string
For solving these errors the configuration must be fixed:
Error 1-3: can be solved by simple dropping the following lines from ./neoscms/Configuration/Settings.yaml
resource:
publishing: null
fileSystem: null
mirrorMode: copy
Error 4: Fix the configuration in ./neoscms/Packages/Application/TYPO3.Setup/Configuration/Settings.yaml
Typo3SetupProvider:
provider: 'FileBasedSimpleKeyProvider'
providerOptions:
keyName: 'SetupKey'
authenticateRoles: ['TYPO3.Setup:SetupUser']
requestPatterns:_
'TYPO3.Setup:controllerObjectName':_
pattern: ControllerObjectName_
patternOptions:_
controllerObjectNamePattern: 'TYPO3\Setup\Controller\.*|TYPO3\Setup\ViewHelpers\Widget\Controller\.*'
entryPoint: 'WebRedirect'
entryPointOptions:
uri: 'setup/login'
Error 5-6: Fix the configuration in ./neoscms/Packages/Plugins/Flowpack.Neos.FrontendLogin/Configuration/Settings.yaml
Flow:
security:
authentication:
providers:
'Typo3BackendProvider':
requestPatterns:
'Flowpack.Neos.FrontendLogin:NeosBackend':
pattern: Flowpack\Neos\FrontendLogin\Security\NeosRequestPattern
'Flowpack.Neos.FrontendLogin:Frontend':
provider: 'PersistedUsernamePasswordProvider'
requestPatterns:
'Flowpack.Neos.FrontendLogin:NeosFrontend':
pattern: Flowpack\Neos\FrontendLogin\Security\NeosRequestPattern
patternOptions:
matchFrontend: true
After changing this configuration you have to clear the cache and rebuild it:
export FLOW_CONTEXT=Production
./flow flow:cache:flush --force
./flow flow:core:compile && ./flow doctrine:compileproxies && ./flow flow:cache:warmup
I am not sure whether this configuration is made in the right way (for Neos 2.3.8). I just copied and adapted it from Neos 3.2. Anyway the 6 errors were not displayed any more 
The remaining issues can be tracked here: Some editors of inspector cannot be loaded after a fresh installation