Although the version of curl in the Ubuntu repos is sufficiently recent to support HTTP/2, Ubuntu have compiled the packages without nghttp2 support, so if you try and use --http2 you'll probably receive the output curl: (1) Unsupported protocol
This snippet details how to install deps, and then compile curl with http/2 support - it can then be installed alongside, or over the top of the existing curl (alongside is better IMO).
sudo apt-get nghttp2 libnghttp2-dev libssl-dev
wget https://curl.haxx.se/download/curl-7.66.0.tar.gz
tar xzf curl-7.66.0.tar.gz
cd curl-7.66.0/
./configure --with-nghttp2 --with-ssl
make
# If you want to install alongside, and only for you
echo "alias curl-h2=\"$PWD/src/curl --http2 --http2-prior-knowledge\"" >> ~/.bashrc
# Or, alongside but for everyone
echo "alias curl-h2=\"$PWD/src/curl --http2 --http2-prior-knowledge\"" | sudo tee -a /etc/profile
# Or to install over the top
# (will install as curl and you will need to specify --http2 --http2-prior-knowledge )
sudo make install
# Assuming an alias was created
curl-h2 "https://www.bentasker.co.uk" -v -o/dev/null
# If not, then
curl --http2 --http2-prior-knowledge "https://www.bentasker.co.uk" -v -o/dev/null