First of all, I apologize for not answering your specific question about themes but.
To be honest, instead of struggling with themes on XFCE or MATE, you should consider that there isn’t much difference in performance right now between those and Cinnamon or KDE Plasma. Both have a workflow very similar to Windows 10 out of the box, which would make the transition much more painless for your mom.
I highly recommend Linux Mint (Cinnamon Edition); it’s the gold standard for ‘it just works’ and feels like Windows 10 without needing extra themes. If you prefer Plasma, Kubuntu or Tuxedo OS are excellent, stable, and beginner-friendly options that run great on older hardware without being ‘bleeding edge’ or unstable.
First of all, I apologize for not answering your specific question about themes but.
To be honest, instead of struggling with themes on XFCE or MATE, you should consider that there isn’t much difference in performance right now between those and Cinnamon or KDE Plasma. Both have a workflow very similar to Windows 10 out of the box, which would make the transition much more painless for your mom.
I highly recommend Linux Mint (Cinnamon Edition); it’s the gold standard for ‘it just works’ and feels like Windows 10 without needing extra themes. If you prefer Plasma, Kubuntu or Tuxedo OS are excellent, stable, and beginner-friendly options that run great on older hardware without being ‘bleeding edge’ or unstable.