Its seems the error is same as thsi forum:
I had with ticket: 1507321697 as mentioned in this forum, the developer is still investigating this problem.
Could you try to install "Quartus from the installation 19.2 and the Nios II SBT from the installation 18.1"?
Could you try the steps as below:
1. Window search> turn window features on or off> enable Window Subsystem for Linux
2. Restart the computer
3. Go to Microsoft Store install -Ubuntu
4. Open Ubuntu and type the following command:
-sudo apt install wsl
-sudo apt install make
-sudo apt install dos2unix
For more information, you may need to chapter 2.1 in link below:
I am running "real" Ubuntu, not the WSL version. No Windows on the computer, and no need to enable Linux - my system boots Ubuntu 18.04 LTS.
The make system and dos2unix were already installed. (dos2unix is just a text format / end of line changer)
Installing WSL in "real" Ubuntu causes the libxml2-utils package to be installed - and I think that this is what fixed it.
This is with Quartus 18.1.1 - I can't use 19.1 until the JTAG-UART is fixed.
My original question remains: Can the SBT be downloaded separately, or must the full Quartus package be downloaded?
Upon checking in https://fpgasoftware.intel.com/19.1/?edition=pro&platform=windows, the SBT could not download seperately and it is included in Quartus Prime package.
Sorry for make confusion.