So, you want to play in a Middle-earth setting using the rules from 5th edition. There are many other fine games specifically designed for roleplaying in Middle-earth which you may have already considered. After all, 5e is designed for more fantastic magical settings, but it can be done with some effort by both the dungeon master and the players.
These materials below are designed for playing Middle-earth in the Third Age. Choose what you find useful for your own game.
Races and subraces from Middle-earth in the Third Age.
Classes for a low-magic setting like Middle-earth in the Third Age.
The pantheon of the "gods" (Valar) of Middle-earth in the Third Age. This may be useful for cleric or warlock classes, if such classes are used in your setting.
Languages in Middle-earth during the Third Age, and how to use them with the 5e rules.
Stat blocks for creatures and monsters that may be found in Middle-earth in the Third Age.
Middle-earth has a different feel than other fantasy settings, especially when it comes to spellcasting. These simple tweaks may help guide magic users in the right direction.
A simple tweak to traditional invisibility to align it with the world of Middle-earth.
Optional rules for bringing the peril of corruption, a pivotal theme in stories of Middle-earth, to your game.
A compendium of herbs found in Third Age Middle-earth, how they can be found, and their many uses.
Bibelots, mathoms, and magical items from Middle-earth.