Games such as Super Mario Odyssey, Pokémon Scarlet/Violet, and The Legend of Zelda Echoes of Wisdom will receive free updates on Switch 2, including improved framerate and image quality, HDR support, Game Share, and mouse controls.

https://www.nintendo.com/en-ca/gaming-systems/switch-2/transfer-guide/games-with-free-updates/

Arms - Visuals (TV and Portable Resolution), Framerate, HDR

Big Brain Academy - 4 peoples in party mode, GameShare

Captain Toad - Visuals (TV and Portable Resolution), HDR, GameShare

Clubhouse Games - 4 peoples can play 34 games, GameShare

Game Builder Garage - Visuals (TV and Portable Resolution), Mouse Controls

New Super Mario Bros. U Deluxe - Visuals (TV and Portable Resolution),

Pokémon Scarlet & Violet - Visuals (TV and Portable Resolution), Framerate

Super Mario 3D World - Visuals (TV and Portable Resolution), Framerate, HDR (Bowser's Fury only), Gameshare

Super Mario Odyssey - Visuals (TV and Portable Resolution), HDR, Gameshare

Legend of Zelda: Echoes of Wisdom - Visuals (TV and Portable Resolution), HDR

Legend of Zelda: Link’s Awakening - Visuals (TV and Portable Resolution), HDR

Finally, some more details about improvements.

Pokemon Scarlet/Violet - improved framerate!!! lol

Edit: Oh no, Link's Awakening remake doesnt feature improved framerate, only resolution.

Xenoblade 2. Bayonetta 3. Astral Chain need them.

Probably a locked 30fps instead of the sub 30-fps drops we had.

I am okay with that, it's a good looking game that will benefit from proper 1080P/2160P.

I'm more interested in the improvements that any Switch game will have by just running on a Switch 2. Nintendo pretty much confirmed we should expect some upgrades if the game has room for it (dynamic resolutions, fluctuating framerates, loading times, etc).

Some peoples are lazy, so I recommend to you to put more details in the thread. I'll put the details below, so you can update the thread (of course, just if you want).

The free upgrades will launch on June 5th (Switch 2 launch day), the details:

Arms - Visuals (TV and Portable Resolution), Framerate, HDR

Big Brain Academy - 4 peoples in party mode, GameShare

Captain Toad - Visuals (TV and Portable Resolution), HDR, GameShare

Clubhouse Games - 4 peoples can play 34 games, GameShare

Game Builder Garage - Visuals (TV and Portable Resolution), Mouse Controls

New Super Mario Bros. U Deluxe - Visuals (TV and Portable Resolution),

Pokémon Scarlet & Violet - Visuals (TV and Portable Resolution), Framerate

Super Mario 3D World - Visuals (TV and Portable Resolution), Framerate, HDR (Bowser's Fury only), Gameshare

Super Mario Odyssey - Visuals (TV and Portable Resolution), HDR, Gameshare

Legend of Zelda: Echoes of Wisdom - Visuals (TV and Portable Resolution), HDR

Legend of Zelda: Link’s Awakening - Visuals (TV and Portable Resolution), HDR

Indeed, it was one of my highlights from the NS2 announcement. The move to JIT compilation should bring DRS games that struggled on Switch to their top intended performance. Glad that Nintendo has finally joined this way of dealing with backwards compatibility, instead of their previous hardware solutions.

This shift likely explains why they didn't specifically mention a framerate increase for Link's Awakening. Instead of unlocking the framerate, it's more probable that the JIT compilation will ensure the game consistently hits its target 60fps.

EDIT: FPS target correction.

Did any publisher or studio other than Nintendo announced any upgrades to their games on Switch 2 in the meantime?

Weill, Civilization 7 and Hogwarts Legacy will have paid upgrades (10 bucks each)

Plus Rune Factory!

I was surprised that Hogwarts Legacy is doing it. You got more info here:
https://tech.yahoo.com/gaming/articles/hogwarts-legacy-civilization-7-more-190135112.html