Is it reliable at the router itself? If you connect a computer directly to the router with an Ethernet cable do you get consistent speed readings? It sounds like you may have a Wi-Fi problem and not a speed problem. If you connect a computer directly to the router and get varying speeds then Optimum needs to fix the problem.
Our wifi throughout the house improved significantly when I bought a Google Wi-Fi mesh system. I have three points spaced around the house and it’s a much stronger and more reliable signal than anything I got with the Fios router.
There are a few different mesh systems available. I chose Google for price and I like the tools for managing the network. I’m not super tech-savvy so I think they make it pretty user friendly.
Here’s a CNET article from a week ago that goes through their ratings of the latest mesh systems. You can go from $200 up to a lot more but any of these may solve your bandwidth problem.
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We have 400 mbps Speed with Opimum cable, theoretically, and can't change our provider here. Speed is highly variable, sometimes goes on and off during the day and in various rooms, sometimes in the middle of a Zoom meeting. For example, in an Okla Speedtest 15 minutes ago, it was about 20/20, a few minutes later in the same room, 110/40. Now, in a different room it is 270/40.
We have one extender upstairs that came with Optimum recently, and after our numerous complaints, they gave us a separate Gateway Router. The tv and cable boxes work pretty well at this point. The service seemed to work well for a few years, and then became unreliable. We have had 4 separate service calls over the last few months, to no avail. They checked the wires leading to our outdoor cable box, they frequently check our system, and nothing seems to work for continual reliable service Suggestions?