Except Ukraine has 10x the population of Tibet and a land border with EU countries...

When industrial partnerships are broken, there is no incentive to go back. No trust either, neither from the two sides, neither from companies to government not to shut down the transaction again at the first whim.

My bet is that once Russia is on a black list for everything China is going to keep Russia on a leash. Buy enough from them in yuan to keep them alive, sell to them to get those yuans back, don't make them so rich to be able to rebuild a really worrisome army. And who'll be in the Cremlin will still rule over all of Russia and be rich and happy.

I'd like to hear from someone in Russia to understand if this is a credible endgame.

To be fair, the annexation of Tibet happened at a time where China was irrelevant on the world stage having come out of WW2 and a civil war almost completely ruined. Tibet wasn't recognised internationally as a country at the time because of the KMT claims to it. That's not to say that the CCP's invasion, annexation and suppression should have happened or was moral in any way, but Ukraine today has much more political clout and meaning than Tibet had 70 years ago, because attitudes and the capabilities of the countries involved today were different then than they are now.

The way the escalation might go on, it probably won't matter how long it would last.

Cuba has survived for 50 year by leaching off from other countries, USSR until its fall, then Venezuela with two puppet regimes and when that also failed, Obama threw them Oxygen by opening up.

If we count China out, the all-Russian phone would be in a suitcase form-factor. The best tech process for chip making in Russia is 110nm, even though 90nm was bought a decade ago.