It seems players can Scribe a Spell Scroll from Expanded Spells Lists, But you CAN'T use the Scroll that you've just Scribed in 5e2024. Also, Arcane Trickster and Eldritch Knight could NEVER use a Spell Scroll, which these are bugs I believe.

The updated "Spells Chapter (Chapter 7)" has defined what's a "Class Spell List". A Class Spell List is:

If a spell is on a class's spell list, the class's name appears in the parentheses after the spell's school of magic. Some features add a spell to a character's spell list even if the character isn't a member of a class in the parentheses.

and the description of a Spell Scroll is:

A Spell Scroll (Cantrip) or Spell Scroll (Level 1) is a magic item that bears the words of a cantrip or level 1 spell, respectively determined by the scroll's creator. If the spell is on your class's spell list, you can read the scroll and cast the spell using its normal casting time and without providing any Material components.

and also each Spellcasting Class has a section that literally called "Spell List", which means player's can't use a Spell Scroll even though it was Scribed with a spell that you've prepared form features like Magic Innitiate of Species' Traits like Elf. These spells only are only counted as being in your "character's spell list".

By so far, it seems still acceptable to me but then I suddenly finds out that Arcane Trickster and Eldritch Knight actually could NEVER use a Spell Scroll since their Spellcasting feature has stated:

You prepare the list of level 1+ spells that are available for you to cast with spells. To start, choose three level 1 Wizard spells.
...
Whenever that numbers increases, choose additional Wizard spells until the number of spells on your list matches the number in...

Which means, your class is still the "Rogue/Figher" and your class doesn't own a "Spell List". You don't have your "class's spell list", but instead, all your spells are more like borrowed spells from the Wizard Class, while you happend to have some slots to cast it.

Similar things also happens to those Expanded Spell List. You have those spells and see them as your Sorcerer/Wizard/Druid/Paladin/...'s spells, but those spells still doesn't belong to your "class's spell list", since now they have this term clearly specified in the rules.

And... This is bad, but still understandable to me. Like, yeah they haven't learned with these spells properly with formal training so like they might be able to cast it but can't read the Scrolls... Though the funny thing is JC clarified this back in 5e2014 that Wizard Spell Scrolls "intent" to be usable for these two subclasses, but days earlier JC have just confirmed that all of the older Sage Adices are outdated and does not suitable for 5e2024 rules.

But, then, I checked Prerequisites For Scribe (a Spell Scroll) and find it much more absurd:

To scribe a scroll, you must have proficiency in the Arcana skill or with Calligrapher's Tools and have the spell prepared on each day of the inscription.
...

And... Nothing more! Then what does this mean? This means anyone who has the spell prepared, no matter through Magic Initiate, Species, or Expanded Spell Lists, can Scribe the corresponding Spell to a Scroll if they also have the proficiencies needed--But they CAN'T read it and use it if that spell isn't in their "Class's Spell List".

I can cast it, I can Scribe it, but once I'm done, all the things that I've just written down suddenly become unreadable coded passwords that I cannot understand.

What the heck is this?

This was already a really old bug in 5e2014 but few people cared about. I believe this is why designers seem to haven't noticed about this at all. They just copy-pasted the old rules from 5e2014 and clarified some parts in it--Then the bad thing happened.

Even if I can persuade myself with some narratively fine explanations, but this still feels sucks when playing an Arcane Trickster/Eldritch Knight/Any Caster with Expanded Spell Lists and find yourself be able to Scribe some Scrolls you wanna use from your already-prepared-spells but you can't use it.

Sure we can just homerule it as we always have been doing, but it's still a pity for me that this bug is still alive in 5e2024. I'm hoping we'll be able to see new erratas to fix this.

This an interesting analysis. I had always jumped to the idea that you could only read a scroll for a spell that you would have the power to cast (even if not currently prepared) but I hadn't thought about the spells that are granted via subclasses or feats.

When I first encountered the restriction, I was a little curious as to the purpose. Making a spell scroll requires enough planning and downtime and gold that I wonder why it's not like a potion that anyone can use. Or, barring that, why there's not some feature (like proficiency in Arcana) that would let you read any scroll regardless of class.

I certainly think the person who was able to make the scroll should always be able to read and use it.

Acording to the Dev, with the 2014 rules, this was the intent (link to sageadvice.eu), so I guess the same in the 2024 rules:

@cityrat DMG scroll rules: Can Arcane Trickster and Eldritch Wizard use wizard scroll spells level 5 and up?
@JeremyECrawford The intent is yes, the Arcane Trickster and the Eldritch Knight can use scrolls with wizard spells on them.

We have also this answer in the Sage Advice Compendium:

---

Which is correct in the Dungeon Master’s Guide, the rule for scrolls or the rule for a spell scroll?

[...]
For you to meet a spell scroll’s requirement, the spell on the scroll needs to be on whatever spell list is used by your class. Here are two examples. If you’re a cleric, the spell must be on the cleric spell list, and if you’re a fighter with the Eldritch Knight archetype, the spell must be on the wizard spell list, because that is the spell list used by your class.

Yes but Sage Advice has just been confirmed outdated and not usable for 5e2024 days ago, by Jeremy Crawford himself during recent interview...This is the most awkward part.

Quote from SoulknifeInfiltrator >>

Yes but Sage Advice has just been confirmed outdated and not usable for 5e2024 days ago, by Jeremy Crawford himself during recent interview...This is the most awkward part.

 Do you have a link of that interview?

If your Spellcasting feature tells you to use the Wizard list... then the wizard list IS your class' spell list.

Edit: To add, for clarity. What I'm saying is the only reason the Wizard spell list is even the wizard class list is because that's the list their spellcasting feature tells you to use. The name of the lists is superfluous. It only matters what your class feature says. That's your class list. 

I don't see the problem. If you're an EK or AT, your class's spell list is Wizard

If the spell is on your class's spell list, you can read the scroll and cast the spell using its normal casting time and without providing any Material components.

Quote from Ravnodaus >>

If your Spellcasting feature tells you to use the Wizard list... then the wizard list IS your class' spell list.

Edit: To add, for clarity. What I'm saying is the only reason the Wizard spell list is even the wizard class list is because that's the list their spellcasting feature tells you to use. The name of the lists is superfluous. It only matters what your class feature says. That's your class list. 

Yes under the 2014 rules-set there is no issue. Class spell list isn't even a defined concept in the rules. The lists exist and the spellcasting class features refer to them but the concept is never defined and they aren't even mentioned in the spellcasting chapter.

But according to the OP then the new 2024 rules-set will have a set definition and if that definition looks like he claims then I would agree that there is potential for trouble.

Quote from Thezzaruz >>

But according to the OP then the new 2024 rules-set will have a set definition and if that definition looks like he claims then I would agree that there is potential for trouble.

Only if you're deliberately looking for trouble