when trying to edit notes relatively big (for example notes with more than 25 thousand words and 100 thousand characters) with Evernote app inside Android OS the keyboard freezes preventing the user to edit the note. It's not Evernote that freezes, it's the keyboard. I investigated this issue deeply and the keyboard freezes because it is tied to an always-on API that performs accessibility tasks (such as reading out loud, or grammar correction or word prediction) even if all accessibility tasks are disable the API will still be called by the keyboard because that is the norm set by the OS.
So to fix this issue there are a multiple roads that could be taken.I'm gonna give a few examples but use of imagination is free here. Evernote could even contact Google and ask them to take a look at it, maybe they'll fix it on their side by limiting accessibility services time-response to maximum 10 seconds instead of unlimited, or by implementing some on-the-go reading that doesn't freeze the keyboard or by implementing a special treatment to Evernote in particular. Currently accessibility services tries to read the entire note and that's precisely why it takes so long to edit big notes, the bigger the note the longer accessibility services will take to read it, while its reading the note the keyboard freezes and the entire UI stops responding, only after it finishes reading the entire note is that the keyboard starts responding again. It tooks more than 2 minutes, almost 3 minutes for me to be able to edit a note with 131 thousand characters.
That's not to say Evernote is off the hook. Evernote could prevent the keyboard from freezing by dividing notes into predetermined smaller chuncks, all of this happens in the background, the end user will never no this implementation is there, but the patch will enable any Evernote client running in any OS to edit notes with infinite amount of size since a single huge note will actually be constituted of small segments that are put together on-the-fly by the UI renderer.
Evernote could also implement special treatments to the android client application, such as many countermeasures as possible to prevent the keyboard from freezing. For example the keyboard has a special mode that disables accessibility services (the real villain), this mode is often used when remote accessing a PC, you might have noticed when you use Teamviewer or Chrome Remote Desktop the keyboard does not predict words, that's because accessibility is disabled. So if an note is too big, there should be an option to activate this keyboard feature for that note in particular, not all notes. The experience will still be bad since word prediction and grammar correction and swiping are DISABLED, so this is not ideal at all, but at least it's something, at least the user will be able to actually edit the note.
Honestly making this topic is embarrassing, because I'm having this issue since 2014 if I recall correctly, and it's been almost 5 years and it hasn't been addressed, nevermind acknowledged. The information i've discovered is rather important to the developers of Evernote because it lifts the weight from the devs of the app to the devs of the operational system particularly devs working in the accessibility services of Android. Then again, it doesn't entirely lifts the blame from Evernote which could start working a fix right now instead of waiting for Google to hear praises from a niche market.
I hope the logs attached here will be sufficient to eliminate the issue in future versions. I've collected a several logfiles throughout my whole investigation, I'd be happy to share them all with any dev willing to tackle this issue, just let me know what you need. Anyways, combined with the information hereby provided, I believe the ones inside the following link will be enough to debug it.