If it's a new service, why tf don't they send a tech out so that you at least have someone there to troubleshoot it rather than going back and forth with their tier 1 support. The tech may not be especially savvy, but he can see that you have multiple devices, hardwired and bypassing the router that gets abysmal speeds using standard tests.
Have you ever done a tracert? I would run a tracert to ookla, Google DNS, a cdn, whatever you can think of and see where it goes. Frontier techs are probably just running a connectivity test from their fiber distribution point/hub directly to your modem. Yeah, no shit it works fine, there is nothing between here and there. Your other tests are actually making multiple hops to reach other networks, and something's slowing it down along the way. You may need to demonstrate that concept to them until they get someone to help you that understands.
Do all the dumbass shit they suggest though, eventually they will hit the end of their script and escalate.