What are some alternatives?
When comparing Mind Map by RealtimeBoard and Materia, you can also consider the following products
Whimsical Mind Maps - Fast & beautiful mind maps with real-time collaboration
Moka - Moka is a Gnome Shell theme that uses simple geometry & basic colouring.
Atina - Simple project management tool
adapta-gtk-theme - An adaptive Gtk+ theme based on Material Design Guidelines - adapta-project/adapta-gtk-theme
productboard - Beautiful and powerful product management.
Dark - Holistic language, editor, and infra for building backends