How to install a mouse cursor on the XFCE Desktop Environment? [duplicate]

hi I'm trying to install a theme on Ubuntu Studio 20.04 with Xfce. It is a theme from gnome-look.org

The various online guides for Xubuntu say to go to Whisker Menu > Window Manager to choose a theme, and that this menu is reading /usr/share/themes

But not all the folders there appear in the Window Manager, including the new one I want to add

And there is a second UI/frontend tool in the Menu at Settings > Appearance which shows a slightly different list of themes but also not including the one I've copied to the /usr/share/themes folder. Both menus work.

I tried using Catfish to search for folders containing 'Greybird' and there is also a folder /snap/gtk-common-themes/1514/share/themes, but this doesn't have all the themes of either UI menu and presumably these themese came in with something I installed via Snap

Some online guides mention /.local/usr/share or ~/.themes/ but on my system these folders don't exist

Neither frontend has the option to add/install a theme or says where it is looking

I tried giving rw permissions on the new folders but this doesn't seem to make them appear in the UI.

Are there certain files that must be present in the theme's directory for the UI to pick it up? (if so this would have been important for the online guides to have mentioned) some of the ones my UI recognizes had a .theme file inside, but not all of them and I didn't notice something common to all.

Should I install xfce-theme-manager or is that deprecated? I worry it would just give an extra broken UI and folders.

Or since it is Xfce is there a config file where the paths to the downloaded themes can be typed in?

Thanks for your time xx Catty

I think I have worked this out

On this PC I must create a new folder ~/.themes

Themes in this folder are visible to Window Manager, but not Appearance

The folders for each theme must contain an xfwm4 subfolder If themes are packed together in a folder, they must be taken out of the packed folder so that the xfwm4 subfolders are directly inside and exactly one layer down from ~/.themes/

And cursor themes work the same way but the folder to create for them is ~/.icons and they must have a subfolder called cursors and they have also a file called index.theme. Cursors are selected from the Whisker Menu: Mouse and Touchpad.

It's all very... bitty. The Xfce wiki at https://wiki.xfce.org/howto/install_new_themes doesn't mention that these folders must be created if they are initially not there, or say therefore where the pre-installed themes are stored. Or that ~/.themes is only for that user while both ${sysprefix}/local/share/themes AND /usr/share/themes are for all users on the system.

It's unclear to me why there are two different UIs for selecting the theme. I guess it might be an artefact of having installed Xfce on top of Ubuntu Studio?

And keeping the cursors in ~/.icons is obscure. And Firefox has had the ability to browse, download and install themes from the web for what, 10 years?