Hi GetMem, I did some changes in new BGRAControls v4.4 so Linux users don't need to install anything to run BGRAControls by default. This is the changelog:
Since v4.4 the components TBCDefaultThemeManager, TBCKeyboard and TBCNumericKeyboard are not installed by default to allow Linux users to get a seamless installation with the Online Package Manager, not installing third party stuff. If you want these components turn on the "Register unit" in the package options for each file (bcdefaulthememanager.pas, bckeyboard.pas, bcnumerickeyboard.pas) then compile and rebuild Lazarus. On Linux you need to install libxtst-dev and libgl-dev first.
If you can please update the package in the Online Package Manager so anyone interested can benefit from it.
Also I know that some components did not install as well on macOS (these virtual keyboard controls) due to don't have proper working code in 'mouseandkeyinput' that is shipped with bgracontrols, don't know if the one shipped with lazarus has a fix for that.
BTW these controls I think no one is using them, but if one is using can easily turn them on.
I did not need to install libgl-dev because I not checked the opengl package from BGRABitmap.