Proxy or Network Tool
Allow newer Java Edition clients to connect to older servers.
ViaVersion is a Minecraft multi-version support plugin for Paper, Velocity, BungeeCord, Folia, Fabric and Sponge, listed under Multi-Version Support Plugins. It lists support for Minecraft 26.3 and 26.2. It is free.
From the source listing
ViaVersion translates the network protocol so clients on a newer Minecraft version can join a server running an older one. It runs on Paper, Folia, Fabric, Sponge and the Velocity and BungeeCord proxies, and it is the base that ViaBackwards and ViaRewind extend. It is published under the GPL.
From the source listing
Same category
Most recently approved first. This is not a recommendation or a ranking.
Multi-Version Support Plugins · Proxy or Network Tool · by ViaVersion
A ViaVersion addon that allows 1.8.x and 1.7.x clients to join servers on newer versions.
Paper · Velocity · BungeeCord · +3MC 26.3 · 26.2
Cross-version support · Folia support · +2
Multi-Version Support Plugins · Proxy or Network Tool · by ViaVersion
An addon for ViaVersion that lets older Java Edition clients connect to newer servers.
Paper · Velocity · BungeeCord · +3MC 26.3 · 26.2
Cross-version support · Folia support · +2
Minecraft Proxy Software · Proxy or Network Tool · by Minekube
A Minecraft proxy written in Go for Java and Bedrock networks, with multi-version support and a small memory footprint.
Bedrock / Geyser support · Cross-version support · +1
Guides
Connect several servers behind one address, and make sure nobody can walk around the proxy: modern forwarding, firewalls and the exact settings.