Thank you very much for your help and for guiding me through the diagnosis.
After monitoring the system during calculations, it appears that the bottleneck is disk I/O rather than memory or CPU. openLCA uses around 1.5 GB of RAM, while disk activity is very high during calculations.
For context, openLCA and ecoinvent are installed on an HDD on my machine, whereas a colleague using a NVMe SSD (Kingston NV2) does not experience these performance issues.
This likely explains the difference in performance. I will look into migrating the installation to an SSD.
Thank you again for your time and support.