Google Chat requires JSON data of specific schema; the regular alert manager webhook payload doesn’t match it. You need to run an additional process, such as alertmanager-gchat-integration or calert, to transform the webhook payload to Google Chat. Or send it to something like zapier where you transform the alertmanager payload and then forward it to Google Chat.
SigNoz is an open-source APM. It helps developers monitor their applications & troubleshoot problems, an open-source alternative to DataDog, NewRelic, etc.