
Per my research, proxyAddresses is not recommended to retrieve group id. Some proxyAddresses of groups are not set, so we are unable to get the properties. You can refer to the following document
User doesn't have the mailNickName or proxyAddresses attribute set
Currently the best way to get group id is to filter by mailNickname or displayName. Please refer to the following api
https://graph.microsoft.com/v1.0/groups?$filter=startswith(displayName,'Test')
https://graph.microsoft.com/v1.0/groups?$filter=mailNickname eq 'Test'&$select=id
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