Here’s a quick script to tail the nextcloud log and pare down the output to make it manageable in a terminal. It depends on jq (https://github.com/stedolan/jq) being installed.
tail -f data/nextcloud.log | \
jq -r '"\(.app) at \(.time)\n\(.url) \(.message.Exception)\n\(.message.Message)\n\(.message.File):\(.message.Line)"'