Brecher's Inventory Sorting is meant to be a lightweight, vanilla-friendly mod that adds some QoL to inventories, including simple sorting options (by name, quantity, mod) to inventories via a simple click as well as buttons for bulk operations (deposit/withdraw all, matching).
The mod is server-side required, but client-side optional, so that 100% vanilla clients can still connect to your server if players don't want to use it.