But the main point is they need stuff they can operate. They're going to have huge maintenance problems. If they do want modern fighters they should've gone for lighter and simpler fighters. The Su-30s are definitely an overkill for anything in the region, but the numbers are critically small. I'm not sure they're a credible deterrent to Sudan, given that Sudan operates iirc 24 Fulcrums, and dozens of older 3rd gen fighters.
Besides that having these birds might give the enemy goosebumps on the other hand if Egypt wanted to attack Uganda then there is really nothing Uganda can do.
It would be over in a matter of days if not hours, keep in mind that Egypt has a far more superior army and airforce and has significant numbers to do the job.
So unless Uganda is going to buy at least 20 more SU-30 (which they can never affort) their new bought deterrence does only provide a false sense of security, and drains their already bad cash flow not to mention if they got into a war with for example Egypt then those SU-30's would make a very expensive fireworks.
So IMO there is literally noone in the region that would have the power to invade Uganda and get away with it and those who can do have a army and airforce that much bigger that it would make little difference if Uganda would have SU-30's or not.
I hope you understand my point.
The true difference for Uganda can be gained by getting better Ground forces which includes IFV's, AV's + Meduim and Short Range Anti Air assets Tanks, Heli's and perhaps a good amount of short range and medium range fire support iee mortars and artillery. (which is also way more easy to support and maintain.)
I believe that that would boost their deterrence a hell of a lot more then just 4 SU-30's not to mention the fact that even if they would buy second hand ground or perhaps in some cases third hands gear it would already be a major boost to their overall capability as online sources say that Uganda's army has been stuck in the late 70's and mid 80's.
It would grant their army also a great leap forward in mobility which will proof a key point in any war for them, Not to mention the fact that most of the war will be fought on the ground in the bushes where fighter jets become near useless given the terrain of Uganda.