Not all mail receivers provide Forensic Reports.
Many of them send back Aggregate Reports which can be found under the Reports section of the tool, however, not many send Forensics as they require more processing power on their side. Therefore, it is normal to see very little or no Forensic Reports at all for your account.
We are currently one of two providers that have a special feed with Verizon Media Group, which is why you may only see forensic reports from Yahoo and AOL.
It is not a limitation related to our OnDMARC tool or trial account, it is simply a limitation on the recipient's side. Having said that the Aggregate Reports alone are enough to gain visibility and configure your legitimate sources correctly with SPF and DKIM.
We expect that more receivers will provide forensic reports in the future.