My question was not answered:
Is there an upgrade option
from Shark LT
I had looked at the website as well.
It had no info on such an upgrade.
You apparently re-discovered this for yourself.
Since you added no new knowledge, nor did you advance my cause, I am reluctant to advocate your efforts. Sorry.
I have not yet bought LT but I may do so if an upgrade option exists for the future.
No. I am expecting to 'make do' with LT until I can find the budget to UPGRADE to FX.