I installed using pacman.
sudo pacman -S elasticsearch
Btw, Head plugin did work.
sudo /usr/bin/elasticsearch-plugin install mobz/elasticsearch-head
test: http://localhost:9200/_plugin/head/ displays the plugin
So, not sure why marvel displays a white screen (and maybe a 404 error)
If I list the plugins, both are there:
cd /usr/share/elasticsearch
ls plugins/
head license marvel-agent