This datapack lets you individually turn on keepInventory for players, instead of only being able to do it globally, with /gamerule keepInventory, however, it only fully retains your items and you still lose the usual amount of experience.

To turn on keepInventory for a player, use /execute as <Player> run function keepinv:keepinv_on, use [...]:keepinv_off to turn it back off.

Warning: This does not work for void deaths, as those delete your items immediately upon death. If you wish to do something against this, you could use one of my other datapacks - Anti-Void
This datapack forceloads the chunk at 0 0. If you remove this forceload, it will cease to function consistently.