In 7.5, Math's Elements panel was moved to the sidebar, and a new Properties panel was added with the Fonts, Font size, Spacing and Alignment buttons: these buttons don't work from the panel, clicking on them does not do anything, their functions are only accessible from the Format menu. Version: 7.5.0.0.alpha1 (X86_64) / LibreOffice Community Build ID: 2b4d136b65bc79a1248876160e85fab79d52d5d6 CPU threads: 8; OS: Linux 5.14; UI render: default; VCL: kf5 (cairo+xcb) Locale: es-ES (es_ES.UTF-8); UI: en-US Calc: threaded The same happens with the gtk3 UI.
Can not confirm on Windows builds, the sm Formula module Sidebar decks 'Properties' and 'Elements' both function as expected. No dependence on the main menu Format menu. Version: 7.5.0.0.alpha1 (X86_64) / LibreOffice Community Build ID: 2b4d136b65bc79a1248876160e85fab79d52d5d6 CPU threads: 8; OS: Windows 10.0 Build 19044; UI render: Skia/Vulkan; VCL: win Locale: en-US (en_US); UI: en-US Calc: CL threaded
I can't reproduce with: Version: 7.5.0.0.alpha1+ (X86_64) / LibreOffice Community Build ID: 6d6a2343b1d45695f3ea02818d317a022a7b259f CPU threads: 8; OS: Linux 5.15; UI render: default; VCL: gtk3 Locale: en-AU (en_AU.UTF-8); UI: en-US Calc: threaded Nor with: Version: 7.5.0.0.alpha1+ (X86_64) / LibreOffice Community Build ID: c9e961e6803a70587bd4686d05abdd4ac11de434 CPU threads: 8; OS: Linux 5.15; UI render: default; VCL: kf5 (cairo+xcb) Locale: en-AU (en_AU.UTF-8); UI: en-US Calc: threaded Could you please try in safe mode?
I did some more tests. When calling Math as a stand alone app, buttons on the side bar work as intended, but when calling Math from Writer (Insert → OLE Object → Formula Object), they don't. Same problem when calling Math from within Draw. It seems the problem arises when Math is embedded in another module. Maybe you tested Math as a stand alone app? I never use Math that way (it's not intended to be used that way).
*** This bug has been marked as a duplicate of bug 150940 ***