Report Distribution is the primary way to achieve this so if this didn't work for you, we'd need some more details on what went wrong there. That also might be better suited for a tech support case as well rather than trying to resolve in the communities.
If you're on Viya 4, the next best alternative is to use the Rest APIs to do this, which is what you probably meant by HTTP request? The /visualAnalytics/reports/<report_ID>/pdf api will do it and then scripting the email job to send it out to anyone you'd like. However this can be a somewhat complicated approach if you're unfamiliar with using these APIs. But if you say you tried it and the PDF doesn't open, then we'd need more details here on what exactly you were doing. Again depending on how complex troubleshooting this gets, this might also be better suited for a tech support case.
Beyond that, I do not think there are any other options to automatically generate and email a PDF of a report.
