I believe that chrome also has the Java plug-in disabled by default for a while now. The ASDM release notes don't mention Ubuntu, but does mention other Linux distros. You could try installing the ASDM if this gives you an option. Try the latest 7.7 which should have all the bug fixes.
It's been a while but I've installed and run ASDM on Ubuntu 10.04 LTS release.
As Rahul mentioned, it's 99% of the time a browser and Java issue that trips you up. If you update your Java and ASDM to the respective latest versions (though I'd back off one on ASDM TO 7.6(2)), you should have good compatibility.
If you can get the JNLP file to download then you can save and launch it locally as a Java Web Start app.
I just labbed it up and that worked fine. First I downloaded Java from Oracle and followed the instructions to enable it in Firefox. That allows Firefox to recognize Java is installed and it will then give you the option for downloading the JNLP file when you browse to your ASA address with /admin appended for management.
Then install the plugin:
apt install icedtea-netx
Then after it installs, run the jnlp file from your ASA using javaws:
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...