For LineageOS at the very least, you might be able to find an unofficial ROM for your device over at XDA developers forums. There are often ones built for less popular phones, but they don’t have as much frontline support as the supported devices listed on the LineageOS site.
…but it’s exactly as I said earlier. There are technical walls to scale, including whether or not you even have access to the right hardware to start the process to begin with. It sounds like you learned a bunch today, which is good, and hopefully you can either find an unofficial ROM that works for you, or you can eventually invest in a phone that fits one of the ecosystems that you would like to pursue.