How do I upgrade an Android phone's version from my pc

I have Android 7.0 and I'm trying to upgrade it to Android 8 or 9 because some apps require that as the minimum version. The problem now is I feel like my phone has stopped receiving updates from the manufacturer so I want to know if it is possible to manually upgrade it through ADB (or something) with my laptop. When I check the phone's software updater it says there are no upgrades and it's the latest version but we both know that isn't true, so I'm trying to forcefully upgrade it. My phone is T-Mobile and the model is 5049W **Edit:** It doesn't even seem like there's a custom ROM/recovery for this particular model of T-Mobile.