Starting with two fresh nodes A and B: If you start node A and (before node A completes IBD) start a second node B with -addnode={address of node A}, node B will stall and not proceed in IBD.
mkdir -p /tmp/nodea /tmp/nodeb
cat > /tmp/nodea/bitcoin.conf << EOF
prune=1000
bind=127.0.0.1:8333
EOF
cat > /tmp/nodeb/bitcoin.conf << EOF
prune=1000
rpcport=18331
bind=127.0.0.1:18335
addnode=127.0.0.1:8333
EOF
and then start both nodes however you prefer, e.g.
bitcoind -datadir=/tmp/nodea --daemonwait
bitcoind -datadir=/tmp/nodeb --daemonwait
And node B will not advance:
tail /tmp/nodeb/debug.log
Shutdown node A and node B comes to life!:
bitcoin-cli -datadir=/tmp/nodea stop
tail /tmp/nodeb/debug.log