I Died, My Items Didn't (IDMID)

This mod makes so that the items that are dropped on player death are not despawnable. The items can still burn in lava or get lost in the void, but they will not despawn because of item age timer whatsoever. This does not affect mob drops, or items that were thrown out manually.

For Modpack creators, there is a tag called force_despawn that you can modify using datapacks so that you can re-enable despawn for vanilla or modded items. You can find the datapack template here. I suggest using this mod in pair with I Died, My Xp Didn't as a less cheaty alternative to grave mods.