I've ridden in the Ukraine, and also through all the Balkan countries and Turkey.
For me, there's no question at all that I would take the Balkan - Turkey route and avoid Ukraine & Russia.
The Balkan countries are all very interesting and very pleasant places to go through. The further south you go in the Balkans, the cheaper food, fuel, and lodging gets.
Greece is a bit of a disappointment (and also extraordinarily expensive), but you can easily ride from Macedonia (now called North Macedonia, I think) to Turkey in a day. Alternatively, you could ride through Bulgaria into Turkey, but if you went that way, you would miss some really good riding in Bosnia-Herzegovina, Montenegro, Kosovo, and North Macedonia. Bulgaria is flat as a pancake and not at all as interesting as the Balkans.
Turkey is an interesting and pleasant country, except that the traffic in Istanbul is absolutely horrible. If you don't intend to spend time in Istanbul, plan to get up at about 3 in the morning and start your commute from one side of Istanbul to the other then - that way, it will only take you about 4 hours, instead of 12 hours, to cross the city, and you will have a better chance at coming out the other side of the city still alive rather than squashed under a truck.
I've been to Ukraine several times, most recently in 2018. The roads are rough, personal security is a concern, security of the motorcycle is a concern, and there is still a low-key conflict taking place in the south-eastern part of the country. The cops are corrupt, and it takes hours (literally) to cross the border into or out of Ukraine.
As for Russia - I have not traveled by motorcycle in Russia, but I have done a lot of cross-country as a pilot of an aircraft in Russia. Much like Ukraine, customs and border crossing procedures are laborious and a real PITA. The Turks are meticulous about border procedures, but as long as you have all your paperwork in order, they are pleasant and efficient. Border procedures at both Ukraine and Russia are anything but pleasant and efficient.
Be aware that if you route through the Balkans and Turkey, you'll be buying insurance at just about every border crossing, unless you can somehow get your insurance company to add those countries to your Green Card document. Here's a link to a post that explains
Balkans Insurance. That post is 6 years old, but not much has changed since I wrote it.
Michael