Domino server V14.x upgrade or update failed with error – unexpected operator on Ubuntu OS

When starting the upgrade or update, you notice the following errors: ./install grep: osystem: No such file or directory ./install: 199: [: !=: exexpected operator ./install: 44: [: /local/install/fp1/linux64/tools/-E: unexpected operator ./install: 51: [: /local/install/fp1/linux64/tools/-e: unexpected operator ./install: 57: [: /local/install/fp1/linux64/tools/-e: unexpected operator The Domino install script uses #!/bin/sh for the shell. Ubuntu uses bash.
This is a companion discussion topic for the original entry at https://www.angioni.nl/2025/10/10/domino-server-v14-x-upgrade-or-update-failed-with-error-unexpected-operator-on-ubuntu-os/