Yes, both Lucidchart and Gliffy offer a Free Trial.
Lucidchart is designed for Individuals, Large Enterprises, Medium Business and Small Business.
Gliffy is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Lucidchart Starts at $0 whereas for Gliffy Starts at $8/Month when Billed Yearly.
Some top alternatives to Lucidchart includes Miro, FigJam, SmartDraw, Gliffy, Microsoft Visio, Creately, EDraw Max, DrawSQL, Quick Diagram, diagrams.net, Lucidscale and HackerDraw.
Some top alternatives to Gliffy includes Miro, FigJam, SmartDraw, Cacoo, Microsoft Visio, DrakonHub, Creately, Lucidchart, EDraw Max, DrawSQL, Quick Diagram and diagrams.net.