Not sure what the earliest copy is we have of the Lankavatara Sutra, but wondering if it can be found online for free in copy/pastable text format (i.e. not PDF or image).
Per Wikipedia there's a Multilingual edition, Bibliotheca Polyglotta, University of Oslo. You can use its UI to select how much is displayed -- i.e. one sentence or one chapter at a time, or the whole text at once -- and which laanguages. The Tibetan and Sanskrit versions are in Roman text, plus there seems to be three Chinese versions/editions, written using Chinese characters.
http://www.dsbcproject.org/ has machine-readable Sanskrit editions of various suttas, you could also try browsing there and/or writing to email@example.com to ask them. I think that Laṅkāvatāra Sūtra might be also known as the Saddharmalankavatarasutram.
You're right though that what I see online is mostly non-text image scans.
Is my tibetan link correct do you know? http://www.thlib.org/encyclopedias/literary/canons/kt/catalog.php#cat=d/0108
It might be -- see the "Non-Tibetan Title" -- but I can't read the Tibetan to confirm that.
Also here is a copy from the link you posted:
That more-or-less matches what the Tohoku catalog says on page 25:
I say "more-or-less" because the page numbers match i.e. pages 56 through 191, however the section number is off by one (i.e. 108 instead of 107).