Updated to Version 18.104.22.168 (Build ID: 932b512) from 3.5 using the automated process. The spell checker is available and appears to be working when selected except that it does not pick up any errors ie it says 'complete' but misses every error.
I think this one is more or less a DUP of "Bug 53006 - Autocorrection TWo
INitial CApitals does not work because of bundled extensions problem", root of
the problem is incorrect update for "bundled extensions"
please feel free to reopen this Bug if you find evidence that we have an
independent issue here. Indicator might be that renaming of folder "bundled"
under "extensions" in User Profile
does not heal your problem.
*** This bug has been marked as a duplicate of bug 53006 ***