I think you may be downplaying the Denazify part of it. The fact that Ukraine has continually glorified genocidaires, put up monuments to them, incorporated neo-nazis into their government, armed them, and are supported by NATO, is something the entire world should be alarmed at. For example, Canada's deputy PM is a descendent of them and condones their actions, which is extremely troubling. Poland and the Israel regime have also condemned Ukraine in similar ways for this.

One of the main reasons for the original secession of the Donbass was like you said outright attacks, and attempting to "Ukrainize" the area language wise, which is absurd considering how similar the people are.

The Russian government claims that the invasion was in order to “De-Nazify” Ukraine.

This is really overstated. That reason was given amongst many others. The mass liberal media seized upon it and amplified it to ridicule it, even though it has a solid basis. Stating that was the reason for the invasion is simply false.

These protests involved Neo-Nazi paramilitary groups (which are very common in Ukraine) marching in the streets.

Which are more common in Russia and which didn't make up the bulk of the protests.

What you also fail to mention is that the protests started with Yanukovish breaking an electoral promise: Starting EU accession talks.

The government that emerged afterwards was solidly anti-Russian.

You mean that was elected.

The Ukrainian right wing, btw, saw an electoral loss in 2014, in 2012 Svoboda had 10%, in 2014 Svoboda + Right Sector 7%.

The Ukrainian War started in 2014

Indeed. But not with Ukraine bombing anything, but Russia annexing Crimea and sending little green men to Luhansk and Donbas. The "revolutions" there were Russian astroturf.

If you think that "Ukraine shelled Russians in the Donbas for eight years" then, how to put it best, take it up with Prigoshin. As well as reality. The reason Ukraine had so much trouble defending against that part of the invasion was precisely because it could not be met with military force. A police response would've been proper but by the time they figured that one out the Russian agents had already solidified their position.

The Russian government claims that the invasion was in order to “De-Nazify” Ukraine. The motivation to protect the Russian ethnic minority was also clear, but since Russia is a multi-ethnic federation, saying this sort of thing is a political no-no in Russia.

Ukraine is multi-ethnic, too. And no that isn't a taboo in Russia in the least. Everybody knows that Shoigu survived the shark tank that is the Kremlin because, as a Tuvan, he is no threat to whoever is currently president. Russia with a Tuvan head of state is unthinkable.

Zelensky, btw, is ethnically Russian.

The reason you hear "de-nazify" has nothing to do with actual Nazis, that's not how the word is used in Russia. It's simply "the enemy". Hence why they manage to call a Jew a Nazi. There's a lot of words which have strange meanings in Russia due to complete lack of political education. When Putin is saying "de-nazify" he's not talking to people who read Umberto Eco.

In reality, Russia invaded because Ukraine was considering membership in NATO.

That's part of it but not at all all. Ukraine was perfectly willing to let go of any NATO aspirations in the beginning of the invasion if Russia withdrew from Ukrainian territory (there would still be the EU, which is also a defensive alliance, but at least the Yanks would be out of the picture), Russia wasn't interested, what we instead got was Bucha so the option is off the table because no Ukrainian, no matter the ethnicity, believes any more that they will be safe outside of a 110% integration with the west.

There's another reason: Russian national mythos doesn't recognise Ukrainians as a separate ethnicity -- if you allow there to be a separate ethnicity Moscow couldn't claim to be the rightful successor to the Kyivan Rus, any more, a core aspect of its "justification" for imperialism ("Rightful ruler of all the Slavs here, and more"). The Russian empire never tolerated Ukraine as a place that should exist independently. If you want to read up on history, start in the 15th century with the Russification policies of the Empire. Russia has no such interest in Georgia.

This was done because, if they allowed Georgia into NATO, it would require NATO to defend Georgia; since NATO membership requires approval of all existing members, there is always going to be at least one member who is not eager for immediate war with Russia.

That's not how that works. If necessary NATO would have said "...excluding already occupied territories".