This is a server side only fabric mod, that dynamically adjusts the render and simulation distance based on the servers performance.
/renderdistance current shows you the current simulation and render distance (Can be executed by non OP players as well)
/renderdistance fixed ratio|render|simulation <value>|auto sets the render/simulation distance or ratio to a fixed value
/renderdistance limit render|simulation <min> <max> sets minimum and maximum render/simulation distance
/renderdistance mspt shows the average MSPT over the last interval
/renderdistance tps shows the average TPS over the last interval