Can I use an RSA SecurID software token on Ubuntu Linux?

There isn't a RSA Software token for linux, so you will need to resort to using Wine (or running windows in a virtual machine). There is a thread here where the Wine version and RSA Software version detailed that has been found to work.

Another alternative would be to get a phone based token so you are not reliant on a specific desktop and the flakiness of wine. Most phone platforms are supported.

Recent versions of Ubuntu offer the stoken package, a native open source SecurID implementation that includes a CLI, a GTK+ GUI, and a library API.

For more information see the project homepage.