Recommended Mods

Table of Contents

Engine

Morrowind Code Patch (MCP) - Hrnchamd
Incompatible with OpenMW
Modifies Morrowind's exe to fix bugs and optimize things. This allows you to scale up the map to show TR's landmass, but still being a fixed size.

Morrowind Graphics Extender XE (MGE XE) - Hrnchamd
Incompatible with OpenMW
Allows Morrowind to render distant views, scenery shadows, high quality shaders, UI scaling and other features. Works with the original engine, so can be combined with the Morrowind Code Patch but will not work with OpenMW.

OpenMW - OpenMW team
Incompatible with MCP and MGE XE
An open source engine replacer for Morrowind, fixing many bugs with Morrowind's engine. OpenMW allows for better performance of Tamriel Rebuilt on modern hardware. It also allows the map to be as big as your mods need it to be, at a higher resolution than MCP.

Bug fixes

Patch for Purists - Half11
Patch for Purists supersedes the Morrowind Patch Project/Unofficial Morrowind Patch at this time by still being maintained and limiting itself strictly to bug fixes, with gameplay changes confined to optional plugins. Notably has implemented some bug fixes in coordination with TR and the PT mods.

Morrowind Optimization Patch - Remiros & Greatness7
This mod greatly improves outdoor (and to a degree indoor) performance in Morrowind, as well as fixing a lot of errors related to flora.

Project Atlas - Melchior Dahrk and the Project Atlas Team
An extension of Morrowind Optimization Patch which makes models use only one texture instead of many, improving performance. Install after Morrowind Optimization Patch.

Essentials

Better Expansion Implementations - Half11
Fixes overly enthusiastic expansion hooks by delaying the Dark Brotherhood attacks (for Tribunal) and limiting intrustive dialogue topics to a few NPCs (Bloodmoon). Due to its clean and thoughtful implementation, it supersedes most other expansion delayers and anti-nag mods.

Tamriel Rebuilt Original Soundtrack - Rytelier and ASKII
Requires MWSE and MUSE2.
Adds beautiful, original music crafted for TR. Integrates perfectly with vanilla soundtracks and covers the entirety of TR. Requires MUSE2, which allows the tracks to be region, location, and activity-specific.

Project Tamriel

Skyrim: Home of the Nords - SHotN Team
Adds in a portion of Skyrim into the game: the Reach near Markarth.

Province: Cyrodiil - P:C Team
Adds in the island Stirk located west of Anvil.

Graphics

Near Vanilla Road Sign Replacer -  Atrayonis
A mod for the few people who want to keep graphics as close to vanilla as possible, yet still don't like the illegible road signs that shipped with Morrowind GotY.
Covers Tamriel Rebuilt lands as well as Vvardenfell.

Arukinn-Style Signposts for Tamriel Rebuilt - Red Furry Demon
Requires Arukinn’s Better Banner Signs and Signposts
This mod replaces all the road signs on the mainland with readable ones similar to those in Arukinn's Better Banners Signs and Signposts. The style isn't exactly the same (would you expect one Mer paint ALL the signs in Morrowind?), but I hope it's close enough. Texture size is 1024x512.

Unique Tavern Signs for Tamriel Rebuilt - Rats
A mod that replaces the Imperial tavern signs in Tamriel Rebuilt with unique ones for each tavern. Two versions exist, one colored and one with vanilla-style signs. The colored one goes well with Unique Banners and Signs.

Intelligent Textures - Remiros
The easiest way to make the vanilla game consistent with high-resolution Tamriel_Data. Using AI upscaling, nearly all textures of the original game are updated to a 1024x1024 resolution while remaining crisp. The difference between this mod and earlier AI-based attempts is that every texture is carefully curated; textures that upscaled poorly were replaced with hand-crafted versions close to vanilla style.

Grass

Aesthesia Groundcover - Rytelier
Requires MGE XE
Makes every landscape covered in rich grass, made with vanilla aesthetics in HD. Lands will feel fuller and more lively with minimal to no performance cost on average PC.

Remiros’ Groundcover - Remiros
Requires MGE XE
This mod adds high quality grass and groundcover to almost all regions in the game as well as all Tamriel Rebuilt areas. It also includes modified MGE XE shader files that add support for Vcol-based distortion for groundcover objects. This is absolutely required for this mod to function correctly.

Miscellaneous

Anthology Solstheim - Atrayonis
Incompatible with most Solstheim mods
This mod simply moves Solstheim to a lore friendly position, further away from the mainland and Baan Malur in particular.

VSW Remaster: Tomb of the Snow Prince - Wolli and VSW Contributors
Incompatible with Anthology Solstheim and most Solstheim mods
Massively overhauls the hastily-developed Solstheim exteriors in TES3: Bloodmoon, aiming for a quality level consistent with TR and the Project Tamriel mods. New version currently in beta includes Anthology placement and utilizes Tamriel_Data creatures and items to better integrate the island with the province mods. 

Beware the Sixth House, Tribunal Rebalance and Bloodmoon Rebalance - mortimermcmire
The creatures and NPCs in Morrowind's expansions are extremely tough, as they were initially expected to be played with high-level characters that had already beaten the main game. However, this difficulty often doesn't make sense from a worldbuilding perspective in the context of Vvardenfell and TR. These mods correct the issue by rebalancing the expansions. 

Better Dialogue Font - Hrnchamd
This mod makes Morrowind's font clearer without changing the font size.

Better Daedric Font - hardek
“A high resolution replacement for the Daedric font used in scrolls.”

TrueType Fonts for OpenMW - akortunov
Requires OpenMW.
OpenMW is capable of utilizing TrueType fonts instead of Morrowind's font files. This mod consists of a pre-defined setup for three replacement fonts to make users' lives easier.
Use of the optional files Tweaked Texture Buttons and Alternate Pelagiad Font are recommended.

Graphic Herbalism - MWSE and OpenMW Edition - Stuporstar & Greatness7
Requires MWSE Nightly or OpenMW Nightly.
Changes the way you pick plants- instead of opening a container, you simply activate them to harvest their contents, with a visual change upon harvest.
As of Tamriel_Data v7, Tamriel Rebuilt flora supports this functionality natively. As such, the use of this mod is highly recommended.

Weapon Sheathing - TES3 Community
Requires MWSE Nightly or OpenMW Nightly.
Shows equipped but sheathed weapons on a character’s hip or back. Includes sheath and quiver models for the vanilla game.Native support for TR weapons is forthcoming; sheath models are currently being added to the next version of Tamriel_Data.

Glow in the Dahrk -  MelchiorDahrk
Requires MWSE Nightly or OpenMW Nightly.
Neat immersion mod to make windows glow at night in settlements with no performance overhead. TR patch included. 

Perfect Placement  - Hrnchamd
Requires MWSE Nightly.
Lets you move things like in later TES games.