In your opinion as a web developer, what are the best UML tools for Linux?

astah is quite good. http://astah.net/qa/setup/linux

However, if you can afford to buy intellij idea from jetbrains, it has an inbuilt UML tool.

I've used this tool so much before, It's a pretty great!

'Visual Paradigm' Installing Visual Paradigm on linux - link:https://www.visual-paradigm.com/support/documents/vpuserguide/12/14/6043_linuxandunix.html

Try it Out. 

You can use the " UML Designer " plugin on  eclipse

 I also recommend Visual Paradigm  . It has a free community and commercial edition.The Community Edition is totally free   and without time limit. I think its perfect tool to start doing UML .

LUCIDCHART

GENMYMODEL

GLIFFY

CACOO

UMLETINO

StarUML is one of the most popular UML Tool in the world for Linux.

in my opinion, i suggest StarUML, it is open source with rich features and freely available in internet (go to: https://sourceforge.net/projects/staruml/ or http://staruml.io/).

I would recommend the  Visual Paradigm Tool.

Thanks,