Russia looms very large in Balkan politics IOTL, so I wonder how them bordering Serbia, Greece, and Macedonia would go.
This reminds me of a quote by some Russian politician that went something like "if we cannot fly to Serbia, we may soon have to border it".
Below I work off the assumption that this diverges from more or less the modern day.
For one, Serbia has one of the most Russophile populations on earth. It's often said that Serbs love Russia more than Russians do (this has no bearing on my own opinions, and is just a broad trend in Serbian society). Russia is also Serbia's main supporter in the Kosovo Dispute. Russia views Kosovo as a giant American military base in its backyard. I could see Russia ITTL getting a pro-Russian candidate to power in Serbia through a combination of shady methods (bribery, threats) and genuinely huge appeal to a large voting bloc in the county by promising to aid Serbia, even just by supplying it and "militarily guaranteeing no US interference", in "reintegrating Kosovo and Metohija" on the principle that the US won't end the world over kosovo (which notably is not in NATO, largely due to the ongoing dispute with Serbia over whether it's even a country) . Not saying it would necessarily work, but it would certainly create some kinds of interesting tensions. Though without NATO protection kosovo IS defenseless it has no air force, not a single tank, few drones, smaller population, is the 134th strongest, that is to say 11th weakest, military on earth compared to Serbia, the 58th strongest. By no means impressive, but in comparison to kosovo, certainly so ITTL a successful Serbian operation there is... possible. Terrain could be an issue, the West could still find a way to intervene, all depends. This is cyberpunk, so maybe Russia has more Wagner-style mercenary companies eager to be put to work in some war in the Balkans.
Greece has been pretty firmly in the Western camp politically, although friendly with Serbia specifically as far as non or anti Western nations go. Russia, through Bulgaria, will cause SOME kind of drama. Not sure what, but something will be up.
Macedonia is another place with potential for this insanely wanked Russia to build influence. Ethnic Macedonians, particularly those on a broad spectrum between moderately nationalist and ultranationalist, have recently been very angry at the increasing political power being given to the country's Albanian minority. They are especially mad because they see it as "rewarding terrorism", since the Albanians staged an armed separatist uprising in 2001, and as giving Albanians "disproportionate" power. The US, EU, and broader global West are seen as the main advocates for this Albanian empowerment, and have therefore lost face with the Macedonian people, though Macedonians don't tend to be as anti-Western as their northern neighbors the Serbs. IOTL they aren't shifting to Russia because they don't have the same history with Russia Serbia does and Russia is far away (they are becoming increasingly pro Serbian though to face the "common enemy" of Albanian separatism). With Russia on the border though, things change. The big issue, of course, is that Bulgaria is not very popular in Macedonia, and ITTL it sort of seems to be gigaRussia's Balkan wing. Bulgars claim Macedonians are Bulgars, and Macedonians see this as a threat to their independence and an insult. IOTL after Albanian was recognized as a co-official language, Bulgaria asked that the same be done for Bulgarian. This was largely seen in Macedonia as a "further attempt to fracture the country". So the question of whether Russia can win over the hearts and minds of the Macedonians may come down to whether they are more scared of Albanians or Bulgars.
Bordering on Turkey is also geopolitically highly interesting.
Anyway, I wonder what kinds of great games are being played in the Balkans ITTL.