I am trying to install beta 20.04. I am at the installation screen. I selected to install to my 2 tb hard drive with NO formatting. Its been going for 2 1/2 hours. Is that typical?
Keep in mind that is highly recommended to format your hard drive/partition, so Linux won't have problems with it's filesystem format. Often when you choose to not format, it means that your hard drive is already formatted or that it has a suitable filesystem type. If not, that may be the reason why it's taking too long. Reboot and restart the installer and enable formatting this time.
If you still are experiencing issues, your ISO/drive containing Ubuntu Mate may be corrupt and you need to re-download the ISO again.
I got it installed.
But "Indicator Applet Complete has quit unexpectedly" pops up
with every boot up. 
I tried to come up with a way to simulate an Enter to dismiss the message, but had no luck.