Does the Lankavatara Sutra exist anywhere online in Tibetan script, Sanskrit (Devanagari), or Chinese?
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 sanskrit@uwest.edu 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 &quot;Non-Tibetan Title&quot; -- 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 &quot;more-or-less&quot; 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).