Apart from UiPath Community Edition (which is free for lifetime) and Automation Anywhere Trial version, you can also use SikuliX or Sikuli (developed by Sikuli Lab). Its a powerful open source automation tool based on image recognition. So it can automate anything which is displayed on a screen.
It uses python as scripting language and runs on JRE (hence sometimes called as Jython based tool). Its commonly used with Selenium web driver to overcome its limitations, but can also be used to automate any desktop task which needs RPA.
For reference, check the video link: https://www.youtube.com/watch?v=Q2xU2ovoucc