Here is the release order with everything you need:

❤ KH 1.5+2.5 Collection:

1. KH Final Mix (2002)
   
2. KH Re:Chain of Memories (2004) (*)
   
3. KH2 Final Mix (2006)
   
4. KH 358/2 Days (2009) [Cutscene movie]
   
5. KH Birth by Sleep Final Mix (2010)
   
6. KH Re:Coded (2011) [Cutscene movie]

(*) Re:CoM has a particular gameplay, different from the rest of the games. I recommend to play it, but in case you don't enjoy it, watch the cutscenes:
Part 1: https://www.youtube.com/watch?v=X8rJI4EQHe8
Part 2: https://www.youtube.com/watch?v=Sh4HZlU_XbY

❤ KH 2.8 Collection:

1. KH Dream Drop Distance HD (2012)
   
2. KH X Back Cover (2017) [Movie]
   
3. KH 0.2 A Fragmentary Passage (2017)

❤ KH Union X (Part 1: 2016-2018) (Shutdown mobile game, cutscenes only)
Watch up to 2:23:11. It's what was released before KH3.
https://www.youtube.com/watch?v=68lZEYUjtRU

❤ KH3 + ReMind DLC (2019-2020)

❤ KH Melody of Memory (2020) (Rhythm game)
At the moment it's not on Steam. You can buy it on the Epic Store or watch the cutscenes:
https://store.epicgames.com/p/kingdom-hearts-melody-of-memory
https://www.youtube.com/watch?v=74CsyCIQg0E
Read the video description

❤ KH Union X (Part 2: 2019-2021) (Shutdown mobile game, cutscenes only)
Now you can continue from where you stopped (2:23:11), and finish it.
https://youtu.be/68lZEYUjtRU?si=eI1gzQXYA8dnQRvG&t=8593

❤ KH Dark Road (2020-2022) (Mobile game)
You can play this game, but I recommend watching it:
https://www.youtube.com/watch?v=qFOwEM8bygM

1. KH4 (TBA)

I hope you find it helpful.