Unity 2022.3 is a great LTS version to park an older game in maintenance mode on. It's where everything kind of congealed into a solid, reliable engine again, after the hot messes that were 2020.x and 2021.x. It's also still receiving updates for Enterprise users through Unity's xLTS program, which admittedly isn't within reach of most people, but it's a good option for already released, successful games that require continued support.