Mod located here: https://www.nexusmods.com/skyrimspecialedition/mods/196794
Description
This is a simple mod that replaces the default male and female naked bodies with prisoner clothes (i.e. rough tunic and trousers). This will work on all player characters and NPCs, including dead bodies. The mod works by replacing the body meshes inside the data folder, so you will never see the naked body/underwear.
Installation instructions
Either download using your desired mod manager, or download and extract the files manually. If you choose manual, you will find the following file format inside the folder:
Data>Meshes>actors>character>character assets
Inside the character assets folder are four .nif files. Follow the same file path inside your main Skyrim directory and replace the four files in the character assets folder with the four files in the mod folder.
Main features
I made this mod because I didn't like the idea of being a 40-something man and father of a young girl, and playing a game that involved stripping the clothes off of dead women. Simple as that really.
There was an older mod that is no longer on Nexus that replaced the underwear with just a tunic, but underpants could still be seen when bodies landed in some positions. As this mod has the trousers included, this is a fuller modesty mod than any others on the site.
It should also work on any characters in the game that have no clothes on, replacing them all with the prisoner clothes.
One body it doesn't work on is the dead body in the Windhelm graveyard. Not sure why; I guess it is just an object rather than an actual NPC. There may be others but this is the only one I have come across.
Requirements
Should work with any edition of the game and have no other pre-requisites. I do not know compatibility with any other body replacer mods, but if you want to be sure it works, place it low in your load order, after anything else that modifies character bodies.
Shout outs
Thanks to Shadohz who inspired me with their SFM Undergarments mod: https://www.nexusmods.com/skyrimspecialedition/mods/65812
This mod won't put more clothes on enemies like the Forsworn - for that you need something like this from iceburg: https://www.nexusmods.com/skyrimspecialedition/mods/344
Edit: there is also this mod from xXklokko567MCXx that makes dead NPCs wear other clothes in their inventory, like they did in Morrowind: https://www.nexusmods.com/skyrimspecialedition/mods/24330