So I followed the advice given in this post:
viewtopic.php?f=20&t=20741&sid=d550ca73 ... f40042f786

I even started another copy of the play_mp3_example.
I selected the Lyrat V4.2 board in HAL.
Now I get 3 warnings before I change anything:

In Visual Studio Code when building "play_mp3_example" if I have an error like an un-used variable it builds ok but I get a warning message about the un-used variable and another warning on the line: ESP_LOGI(TAG, "[2.2] Create i2s stream to write data to codec chip"); i2s_stream_cfg_t i2s_cfg = I2S...

As a novice:
Where can I find a list of the CMAKE commands please.