Allow 1.8.x and 1.7.x on your newer server
Requires ViaVersion (ViaFabric on Fabric) to be installed
You can find the latest dev builds here:
Jenkins: https://ci.viaversion.com/view/ViaRewind/
Spigot page: https://www.spigotmc.org/resources/viarewind.52109/
CurseForge mod page: https://www.curseforge.com/minecraft/mc-mods/viarewind
Maven: https://repo.viaversion.com/