New system V9 is available at connect section, make sure you refresh the page first ( F5 )
Old system V8 or older will not work, I recommend to delete the old V8 system folder from your Lineage 2 game directory since is not compatible with this new one.
The new system will ask you to disable virtual environment and another windows feature in Windows 11, this is normal so press Yes on both messages and restart PC.
If you do not want to save your account in client simply uncheck the "save accounts".
For other problems please let us know.