this process worked on my raspiblitz:
##start

tor --version #verify <0.4.7.7

dpkg --print-architecture #verify arm64

sudo apt install apt-transport-https

lsb_release -c #verify buster

sudo nano /etc/apt/sources.list.d/tor.list

##add repos

deb [signed-by=/usr/share/keyrings/tor-archive-keyring.gpg] https://deb.torproject.org/torproject.org buster main

deb-src [signed-by=/usr/share/keyrings/tor-archive-keyring.gpg] https://deb.torproject.org/torproject.org buster main

##save

sudo wget -qO- https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89.asc | sudo gpg --dearmor | sudo tee /usr/share/keyrings/tor-archive-keyring.gpg >/dev/null

sudo apt update

sudo apt install tor deb.torproject.org-keyring

sudo apt dist-upgrade -y

tor --version #verify 0.4.7.7

##end