# or use
# sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys BA300B7755AFCFAE
wget -qO - https://typora.io/linux/public-key.asc | sudo apt-key add -
# add Typora's repository
echo -e "\ndeb https://typora.io/linux ./" | sudo tee -a /etc/apt/sources.list
sudo apt-get update
# install typora
sudo apt-get install typora