Ombudsman or Congressional inquiries do not help much. Their clerks have a direct line to speak to USCIS with no wait. That is basically it. USCIS will tell them the same BS that they tell to your own online inquiries.
Mandamus usually takes up to 2 months. But some cases can get resolved in a couple of weeks after summons are served. I work for a law firm and did not really want to file Mandamus for my own case just to not get interviewed, since most Mandamuses lead to an interview. But I'm pissed waiting since it now takes 16 months to process even for RTDs. I feel here like I'm in a golden prison. I want to travel and get medical treatment abroad, otherwise I could wait.