There is a default java that you can set up by the following commands:
sudo apt install default-jre
sudo apt install openjdk-11-jre-headless
sudo apt install openjdk-8-jre-headless
Let me know if it works!
I had trouble getting this to run on Mint 19 due to having Java 11 installed by default and not wanting to set 8 as the default Java. Solved this here: https://unix.stackexchange.com/questions/545041/running-thinkorswim-on-linux-mint-19
Copying answer here for ease of use:
I tried a variety of things but the one thing that seemed to work best
is by ...