TPSMonitor is a client-sided Fabric mod for Minecraft 1.16.4 that reports the current estimated tickrate of the server. The mod does not require any permissions or specific configuration on the server side, i.e. you can use it freely on any server.
Note: TPSMonitor also displays the tickrate when playing singleplayer - the reported TPS refers to the tickrate of the integrated server.
Minecraft 1.16.4 with Fabric is required. Download TPSMonitor here and place it in your /.minecraft/mods
directory.
While in game, the mod simply displays the current TPS (more precisely: average TPS during the last 15 seconds) in the bottom right corner. No configuration is needed.