This is a simple plugin I have made, which allows you to set the keepInventory mechanic in Minecraft in a per-player way, through a permission node.

Server Requirements:

• Java 8 or higher;
• If you use a Bukkit-based server (Craftbukkit/Spigot/Paper/etc...): This was tested in version 1.12.2 of Minecraft; in theory, this should work as far back as 1.8.8 though, and newer versions too;
• If you use a Sponge-based server (SpongeVanilla/SpongeForge/etc...?): This was tested in version 7.3.0 of SpongeVanilla; in theory, as long as your server version supports that API version you should be fine.

How to use it?

WARNING: Do NOT set the keepInventory gamerule to true in the world, through /gamerule or any equivalent command (if you have a world management plugin); this plugin won't work otherwise. If you have already done it, set it to false.

1. Install this plugin and a permission management plugin in your server (LuckPerms is what we recommend!);
2. With the permission management plugin you have installed, give the permission "iki.events.playerdeath.keepinventory" to whoever you want.

Examples:

Assuming you are using LuckPerms:
1 - If you want to give keepInventory to a specific player or group:
2 - If you want to give keepInventory to everyone except a specific player:
And there might be other use-cases I could spend 40 more hours covering here.

Data Collection:
This plugin uses bStats to collect some analytics data about your server, such as its version, plugin version, location, Java version, and others. This data is completely anonymous; nevertheless, you can disable it in "plugins/bStats/config.yml". Note that this will disable data collection for all the plugins that also use bStats.



You can report issues here. I just don't promise to fix them quickly.
Rate the plugin if you like it!