100,000 are believed to have never left. Some who had gone to Russia have been told to return or they will lose their property. People are doing this, unbelievably. They don't necessarily know how bad it is in Mariupol. Then there are Russians who are moving there and taking Ukrainian houses (some of those who have returned from Russia have got there only to find that there is someone else living in their home and they are told that they no longer live in their own home). So three groups - stayers, returners and occupiers.
Re comparisons with Wales, it is important to note the Welsh border has remained static for a considerable length of time. The Ukrainian border has been more fluid in multiple directions so there is some dispute over this but I do think its being massively overstated in whats said by a whenwillwegetthereholly.
The Soviet Union did blur the concept of national identity but it doesn't change what Ukraine was / is in terms of its land. It blurred it by making it possible to be Ukrainian and say accurately you've never left your country and yet technically by todays understanding have lived in multiple countries as we would understand them in 2022. Russian was the language that united these countries, despite multiple languages being spoken across the Soviet Union.
However since Ukrainian independence, I don't think you can say any area is Russian any more than you could do about Finland, Lithuania, Estonia or Latvia. Yes people have moved freely over the border in both directions and have settled either side and have intermarried but you either believe in international law or you don't. If you don't, then you believe in a policy of actively seeking conflict and oppression. The problem here is precisely Ukrainian independence - Russians don't like the concept of self determination. The Moscow elite hold power over its separate regions in a imperial colonialist fashion even today and they believe they have the right to continue to do this (Hence the current war and previous wars in Chechnya and Georgia). Kamil Galeev's reflections on this do it justice better than I do. This is why Ukrainian nationalism has arisen in the first place and is mirrored in the Baltic States who declared Independence in the 1990s and managed to free themselves from Moscow. Belarus, by contrast, is an example of a country which never fully shifted it (There are others). Russia sees this as US interference because it refuses to give credibility to the concept of self determination - it must be the enemy of US, rather than those who were Soviets actively rejecting Moscow. To acknowledge the concept of self determination is dangerous to the imperialistic self interest of Moscow. It cant say 'yeah crack on there being independent and successful' because it opens the possibility of other regions doing the same due to mismanagement and corruption. Its a sign of the weakness of Russia as it stands and the generational issue where there isn't an obvious successor class to Putin and his Allies. When they die, the risk of the country having separatist movements shoots up. Putin is in a sense battling this. He wants a legacy to be one of ongoing Russia reminiscent of the Soviet Era rather than being the 'last Tsar'. (If course you can have a whole argument about the influence of the war on what happens next).
I'm also not getting this shit about Russian land being given to Ukraine. The whole concept is Russian propaganda that needs to be knocked on the head. Its a lame justification for braking international law. I think there is an argument about Crimea to a point - it was given to Ukraine in 1954, but beyond that?
International law isnt purely a western concept - it is universally observed by dictators across the world, and existed before the US was born...
See:
https://en.m.wikipedia.org/wiki/File:Ukraine-growth.png
If you can explain to be, how exactly 40% of Ukrainian land is somehow Russian and Russia has an argument to claim it because of self determination, then please can you crack on with it, with reference to the above map as I'd be delighted to hear this baloney.