The answer by @ROSt52 (and as implied in the question) will generally offer a workaround, but MacOS has long had issues with its treatment of the Alt / Option key and LO has compounded this. First, the symbol used throughout LO to indicate the Alt / Option key is wrong (fdo#39477): ^ means Option rather than Control (which is the usual meaning associated with this symbol). This can be confusing for MacOS users and can give the impression that keyboard shortcuts do not work (fdo#43680). Help file information may not be accurate in this respect.
The answer by @ROSt52 (and as implied in the question) will generally offer a workaround, but MacOS has long had issues with its treatment of the Alt / Option key and LO has compounded this. First, the symbol used throughout LO to indicate the Alt / Option key is wrong (fdo#39477): ^ means is used to indicate Option rather than Control (which is the usual meaning associated with this symbol). This can be confusing for MacOS users and can give the impression that keyboard shortcuts do not work (fdo#43680). Help file information may not be accurate in this respect.