Stern
Stern isn’t that great to use to filter log messages in if you do not know jq/don’t have JSON format available but it is possible to escape characters when you use include.
stern -c istio-proxy -i '\"response_code\":200,' .stern -c istio-proxy -i '\"response_flags\":UH' .stern -c istio-proxy -i '\"response_flags\":\"-\"' .