ViaVersion and ViaBackwards were added to the server to add support for earlier versions of Minecraft going all the way back to 1.17.1. Anybody using versions earlier than that should consider using ViaFabric or ViaForge instead.
ViaFabric (Legacy Fabric 1.8.9 and Fabric 1.14+): https://modrinth.com/mod/viafabric
ViaForge (1.8.9 and 1.12.2): https://www.curseforge.com/minecraft/mc-mods/viaforge
If you are connecting using older versions of Minecraft, do note that you are doing so at your own risk.
ViaFabric (Legacy Fabric 1.8.9 and Fabric 1.14+): https://modrinth.com/mod/viafabric
ViaForge (1.8.9 and 1.12.2): https://www.curseforge.com/minecraft/mc-mods/viaforge
If you are connecting using older versions of Minecraft, do note that you are doing so at your own risk.