If I like Wellington College, where else might I like?

As I said, it is very difficult to find a school without compulsory sport. It is always part of the curriculum so how does any child avoid it? Apart from at Winchester and obviously not all sport haters go there! Sometimes you just have to do what you don't like but what you do like about a school outweighs the sport situation.

My DD1 went to a very sporty school, and we knew she was pretty useless at sport, but the teaching, drama, music and other aspects of the school more than made up for having to do a bit of sport every week. There are always other non sporty children in a school, always. No non sporty boy plays sport with the hench boys - it is just not safe! St Edwards definitely has non sporty boys. Rugby definitely does. I would see if the whole school fits your DS, OP, not just one aspect of it. Also, does the school celebrate other forms of success? Eg Maths Olympiad, Music, Drama, Art, keeping your room tidy, joining in with House activities.... There are lots of aspects to school life that can be celebrated in addition to sport. Good luck

OP a slightly going against the grain POV.
The most important is that he is in a school where he feels comfortable with his set of talents and not a second class citizen or alienated because he dislikes sport.
However for real computer geeks they tend to do it themselves anyway and IT / computer science teaching lags behind what they try out themselves. If I had that sort of DS I would probable want him to develop other important directions, away from his beloved computer, especially as these schools have very long holidays with plenty of time to indulge his passion.

I suppose I am saying that don't discount Winchester as there are plenty of similar boys to your DS and I don't get the impression that restraining their 'computer geekiness' to their own time has held them back in that regard.

Sevenoaks as suggested might well be worth a look as well.

I can't decide from reading their website whether or not rugby is compulsory at Tonbridge but I have heard that ICT is very strong there.

Here is Blundells approach to sport doesn't look very promising from the OPs perspective.
You are going to struggle OP to find a non sporty boarding school.

Have you thought about Sevenoaks School? They do sport but are not a sporty school as such, my son was not that interested and got by but they have very good technology and you can be anyone you want there, there is not a 'type'.

I happen to know rugby is compulsory at Clifton in the early years.

Clifton Coll?
Blundells?

There is no formal IT teaching at Win Coll, boys usually by the end of their 2nd year can use lap tops but the school system prevents gaming etc. I just don't see it as the place for a computer geek which is a shame because it would be perfect from a sporting (or not) point of view.
The problem is that boarding schools need to fill the time and making pupils do sport at least three times a week is one of the ways of doing this. The other often compulsory activity is CCF how do you think he'll feel about that?
What about SPS I think there is no main sport, so lots to choose from, ICT is very strong, they never used to have CCF, and they do flexi/weekly boarding. He would have to significantly work on his organisational skills otherwise he'd drown. You might be too late to register. But might be worth looking at.

I could suggest Win Coll where sport is largely optional, many boys don't do any sport and there is no rugby but I'm not convinced it's the right place for a computer geek, the boys aren't even allowed laptops for at least the first year and half!

Lots of rugby at St Edwards not exactly compulsory as there are other choices; rowing, squash, rowing, rowing, maybe rowing you'd have to find out what the options are but is it really a good choice for the rugby hater?

Sport looms large in all boarding schools! I know non sporty children at Rugby. They seem happy there. St Edwards, Oxford might be worth a look. I find the concept of working 'a year above' rather odd. A year above who or what?

I need to clarify. I'm sure your young pupil was telling you the truth. My point is that successful sportsmen will be more admired by their peers at some schools than at others.

You will find that all schools will tell you that non-sporty boys will thrive but I really do think that rugby runs down Wellington's spine.

Marlborough is full boarding or day only. It's a big school and I don't think is particularly suitable for a geeky/computer nerd. It's sporty, I think rugby which is taken very seriously is compulsory in the early years.
Bradfield is a nice happy caring school and it's weekly boarding, a friend described her DS as "geeky" and not very sporty (unlike his brother) so sent him to Bradfield.
Tonbridge is very sporty but also offers a DT scholarship so might be worth looking into to find out how non sporty geeky types are catered for it too is weekly boarding.

I would not send a non-sporty DS to Wellington. You might like to look at Bradfield?