I want to express that a computer is rarely updated, and that I am in doubt that there will be any update at all. I would like to say it this way:
The computer is unlikely to be updated, if any.
Now the sentence sounds me wrong because it seems as if "if any" would require an amount to be explicitly stated, as in this sentence:
The computer is unlikely to receive any update, if any.
So I wonder whether the first sentence is correct or I should resort to something like... "if even at all"?.
The phrases "if any", "if at all", "if ever", etc. are used to indicate the very minimum occurrence of something. In statements of likelihood or probability, they emphasize that even the bare minimum may be unlikely. However the emphasis only makes sense if it contrasts against the rest of the sentence, so the rest of the statement should deal with more than the bare minimum.
Your example sentences already mention the minimum: "any update" does so explicitly, while "unlikely to be updated" does so implicitly. As such, adding "if any" at the end doesn't really work, because the sentences already convey that meaning without it. Better sentences that include "if any/ever/at all" phrases would be:
The computer is unlikely to be updated much, if at all.
The computer is unlikely to be updated often, if ever.
The computer is unlikely to receive many updates, if any.
In the first sentence, "if at all" is used to contrast with "much". Because this sentence concerns the frequency of an action, "if ever" could be used instead of "if at all", but "if any" would not make sense.
In the second sentence, "if ever" is used to contrast with "often". This sentence also concerns the frequency of an action, so "if at all" would also work, but "if any" would not work here either.
In the third sentence, "if any" is used to contrast with "many". Because this sentence concerns the number of occurrences of a thing, "if ever" and "if at all" would not make sense.
Think of these phrases as a way to say, "It is unlikely that something will happen even a single time, so it is very unlikely that it will happen multiple times.
Where "any" refers to the likelihood of updates rather than to the updates themselves, one could write:
There is little if any likelihood of this computer having been updated.
