This repo (based on the one here) contains .deb files built from the latest version of otc-auth.
sudo curl -SsL -o /etc/apt/trusted.gpg.d/otc-auth_ppa.gpg https://iits-consulting.github.io/ppa/debian/KEY.gpg
sudo curl -SsL -o /etc/apt/sources.list.d/otc-auth.list https://iits-consulting.github.io/ppa/debian/otc-auth.list
cat /etc/apt/trusted.gpg.d/otc-auth_ppa.gpg | gpg --dearmor | tee /etc/apt/trusted.gpg.d/otc-auth_ppa.gpg >/dev/null
sudo apt update
sudo apt install otc-auth