it's somewhat "hidden" under section named "SSH Console".
please pick the correct image for you box in the wget command from here:
Downloads - LibreELEC
in any case backup before !
P.S.
I'm not sure, but I guess you should be able to do the upgrade now also via auto-update by short time activating "Show custom channels" (which should update the contense of the subseq. options/boxes), adjust subseq. options and de-activate "show custom channels" afterwards and then upgrade the box. [1]
P.P.S
don't forget to update your addon's afterwards too
[1]
... if the upgrade from 9.2 to 10 is allowed at all (me came from 10-RC)
+++ EDIT +++
from here:
LibreELEC (Matrix) 10.0.0 - LibreELEC
cit.: "So unless you are already running an image with Kodi 19 inside, a clean install is preferred..."
nightly, RC have kodi 19
and from here (for boxes running generic):
LibreELEC Generic - LibreELEC
LibreELEC 9.2 has Kodi 18.9
combining both sentences:
- clean install for an upgrade from 9.2 to 10 is preferred
- but an upgrade from 9.2 to 10 is also allowed, but could fail
...
I will wait a few months to make a second attempt at installing LE 10.0.0.
I guess doing so would change anything, cause the update procedure stays the same for LE 10 and LE 11 is out then