echo "deb [signed-by=/usr/share/keyrings/halacs.hu.key] https://apt.halacs.hu/apt halacs stable" | sudo tee /etc/apt/sources.list.d/halacs.hu.list
wget -q -O - https://apt.halacs.hu/apt/pub.key | sudo tee /usr/share/keyrings/halacs.hu.key

# OR

wget https://apt.halacs.hu/apt/pool/stable/halrepo/halrepo_1.0.0-1.0.0_amd64.deb -O /tmp/halrepo.deb
sudo apt install /tmp/halrepo.deb