The sentence

Except the buildings built towards the end of his life, the buildings erected in Istanbul can be assumed to be his.

was recently used in a question here.

I edited to replace 'except' with the compound preposition 'except for'. I'm very unhappy with the original, but don't like to assume my gut reactions are necessarily correct.

CDO gives:

Except or except for? from English Grammar Today

We often use except and except for as prepositions to mean ‘not including’ or ‘excluding’. They are followed by a noun or noun phrase or a wh-clause. Both except and except for are correct after a noun:

I like all fruit except (for) oranges. (excluding oranges)

Except for Louisa, who’s away in Berlin this weekend, we’ll all be at the party.

She likes going to most sports events, except cricket matches.

This shows the choice of 'Except for' to start a sentence-initial prepositional phrase, but does not go so far as to state that the choice of the simple preposition is incorrect.

The nearest (but really reversed) question I can find on ELU is essentially

Is "Are there any vegetables except for asparagus?" correct?

to which Peter Shor provides the tantalysing answer (with which I largely agree):

I think what's wrong is the "for". [I'd say 'very iffy' in all but some unusual contexts]

Are there any vegetables except asparagus?

The grammar of when to use "except for" and when to use "except" is governed by [a] quite complex set of rules (often, you can use either). There probably is a correct and complete description of how this works somewhere on the internet, but I haven't found it, so I can't tell you why you should use "except" here; but it just feels right.

Can authorities be found giving this correct and complete description of the complex set of rules governing when to use "except for" and when to use "except" , on the internet or elsewhere?