This bug applies to the projectM visualization addon version 2.3.5.1 (and earlier) in LibreELEC versions 9.2, 9.2.1 and (HiassofT) devel 20200320214349-16919f7.
The projectM visualization PRESET PACKS cannot be changed from "projectM" even though preset packs "bltc201, Milkdrop 1.04, Milkdrop 2.00, Mischa's Collection, Stock, Tryptonaut, Yin and Tests" are available from the configuration screen's drop down list. It is possible to select one of these alternatives, but the selection chosen has no effect and the "projectM" preset pack continues to display when listening to music even though an alternative has been selected. Gets a bit boring after a while...