Unfortunately there isn't such option. If you are provisioning Groups/Teams via PowerShell or the Graph API, just add the relevant parameter therein (for example New-UnifiedGroup -AutoSubscribeNewMembers). Otherwise, you need to switch it post-creation.
Also, keep in mind that toggling this setting only applies to newly added members to the Group/Team. Existing members will still not be "subscribed", so if you want to remedy that you need to add them to the subscribers list via Add-UnifiedGroupLinks.