Which support conversations are missable?

In my first playthrough of Fire Emblem Three Houses, I learned that not only support conversations can be prevented due to the story not progressing far enough, but can also be locked out for progressing the story too far. Presumably, this is due to support conversations no longer making sense after certain story events take place, and are met with a "you've missed your opportunity to deepen this bond" message in the support menu.

With subsequent playthroughs in mind, that leads me to a couple of questions...

1. Is there a list of characters & supports that are missable due to story progression (with spoilers in mind, it'd be preferable for listing the chapter number, not the story event, where the support gets locked out)?

2. Does the house/story path you chose matter in determining if/when a support becomes missable? Are there supports that are missable only for a specific house?

This is not a complete answer, but there are at least 2 characters whose supports are missable.

• Edelgard
• Hubert

At 2 different points during Month 3 of the first year (before time skip), you will be given a warning that "This decision will drastically change the story". This requires a C-Support between Byleth and Edelgard. Depending on how you answer both of them...

you will be locked into one of two story paths. In one of these paths, Edelgard and Hubert will both become unavailable as units. Neither Byleth nor any other character can have any additional support with them.

The choices are easy to make, but just in case:

You need to accompany Edelgard to the Imperial capital during one of your Monastery Explorations (on Sunday). This will skip all events until the end of the month.

After the end-of-month mission, you will be told to execute Edelgard. Choose to protect her instead, and you'll be on the Crimson Flower route.

Note that you will no longer be able to recruit any more units at that point, unless you chose the other route: Silver Snow. This will give you another month of time to recruit students.

Obviously, any student you failed to recruit before the time skip will have their support become missable afterwards.

Other than that, I have not yet noticed any missable support conversation.

Note:

I've read that some students you've recruited (e.g. Ashe and Lorentz) do not join automatically after the time skip. If you fail to re-recruit those, their support conversations will also become missable.

Since I failed to recruit either Ashe or Lorentz before the time skip, I couldn't verify this for myself.