The problem is that western media doesnt report any of this, and if you believe in Guardian or any similar newspapers, you will remain ignorant of reality.

If you were to take a look at the Western media, you would see that all these things are actually being reported there. They tell you about the nazis in Donbass (1 2 3), the civilian casualties (1 2) or weapon supplies (1 2).

Russia has tried diplomacy for a long time, it was rejected, [...]

Forcing your interests on a sovereign country is diplomacy in bad faith at best. Putin is an ethno-nationalistic imperialist and it is beyond my understanding why leftists defend him so much (The enemy of my enemy is my friend, huh?)

To understand what Ukronazi means, look at some pictures of the Azov battalion.

Oh i'm fully aware of the Azov battalion and i'm fully aware of nationalist militias parading down the streets for years (source: i know ukrainian political refugees). But do you really think the Russian army is not literally full of neo-nazis too? Just look at the criminalization of antifascism in Russia (many comrades assassinated or in prison) and the abundant footage of actual nazi bands beating up "random" people in the public space... it's nothing new but for some reason you're willing to support an ex-KGB operative (Putin) and his hordes of neo-fascists in the name of fighting against nazis?! What i mean is i don't support the Ukrainian State because i don't support any Nation-State (i'm an anarchist), but i do support anti-colonial struggles, and i cannot ignore the asymmetry of this conflict and the colonial dimension of it (Ukraine is a former colony of Russia). And i cannot ignore that due to a unilateral escalation of conflict, millions of civilians are currently suffering.

there will also be more information about the genocide they carried out for the last 8 years

I know a few people who live in the east of Ukraine (won't say where specifically). Things have been tense and i can't say there hasn't been some forms of political repression on the part of the central ukrainian government, but from what i hear and read (except from russian propaganda) there's nothing that we could even remotely compare to a genocide going on over there. But, even if that were the case, it could justify a so-called "humanitarian" military intervention in affected areas to ensure regional autonomy from the central government, but how does it justify to annex and bomb an entire country?!

Plenty of evidence for an attack, from NATO weapon supplies, constant artillery shelling on civilians

Nation States are trading weapons. What else is new? I mean Russia has also been supplying weapons in this conflict. As much as i despise military activity and weapons trade, i don't see how "A" gives weapons to "B" justifies "C" invading "B". As for shelling on civilians, i'd like a source for that: i'm aware of russia/ukraine cross-fire at the border for years and some civilian facilities on ukraine side being affected, but i'm not aware of a "constant" effort from any side to target "civilians" and i don't think such a thing took place at all.

to even leaked plans and some failed preliminary attacks

Source? And once again, how does that justify invasion? If Ukraine planned to invade Donbass region, the Russian government could have answered Donbass' call for help and sent military protection there. This can never justify an invasion.

Russia has tried diplomacy for a long time, it was rejected

Russia's proposal for "diplomacy" was not a negotiation. It was a list of demands impacting the sovereignty of currently-neutral nations (not aligned with NATO or Russia). I'm personally strongly against both colonial empires, so i'm all in favor of more neutrality, but threatening serious consequences if a third-party nation (which just happens to be your former colony) doesn't comply with your demands is not diplomacy.