had the same,
what worked was chatgpt’s attempt to allow for higher timeout and retries and ipv4 only, worked for me - if all are needed, i havent tested, but allowed me to do it without doing any modifications
sudo apt-get -o Acquire::Retries=10 -o Acquire::http::Timeout=60 -o Acquire::https::Timeout=60 -o Acquire::ForceIPv4=true upgrade --download-only
took a bit, and then upgrade:
sudo apt-get upgrade --no-download