Roole

But in accepting "no authority, including the Soviet authority" they also actively suppressed the domestic Bolshevik movements within the Ukraine.

They accepted no authority but their own, even according to Volin's own testament.

The Red smashed the Black Army because they were a threat. While they were hopelessly outnumbered by the Red Army and in a war of attrition they wouldn't have been able to maintain a front against the Bolsheviks, especially due to critical issues with supply lines and production of materiel, they proved to be a very effective fighting force in the Ukrainian theatre of war in the interwar period.

Or would they be since they show that a stateless society is possible without a transitional state?

Such a loaded question that poisons the well.

Makhnovia had incredibly short-sighted economic policy which risked counterrevolution.

Makhnovia accepted any currency, which is simply disastrous economically and if it persisted as a policy it would have allowed any rich and enterprising aristocrat or bourgeoisie to waltz in and buy up critical goods, capital, land, infrastructure etc. and to re-establish counter-revolution from below. Of course, this wouldn't be allowed to happen because Makhnovia had also directly encouraged rampant banditry so any wealthy prospector would have been executed and their holdings expropriated one way or another in a matter of time however that... doesn't sound particularly anti-authoritarian to me.

But to speak of banditry, Makhno encouraged those who maintained and operated critical infrastructure, such as train lines, to simply charge passing trains and passengers a "fee" for use of the section of network they operated. This would have created the gradual accumulation of wealth in the hands of the more ruthless operators which would have developed into monopoly capitalism if left unchecked.

Have no illusions about it, Makhnovia was state and Makhno was no anti-authoritarian.

Makhno formed a military secret police, known as the Kontrrazvedka, and he used his secret police to surveil and suppress domestic Bolshevik movements. He even used them to execute a network of Bolshevik military leaders in his own army because they proved to be politically inconvenient to his ends.

There was also a clique of military officers which formed around Makhno who ruled by decree, who held contempt for the masses, who directly contravened the authority of democratic political structures within the Makhnovist state, especially but not exclusively the Revolutionary Military Council, and they also engaged in gang rape.

There was also the persecution, ethnic cleansing, and small-scale genocide against German settlers and especially Mennonites in the Ukraine that the Makhnovists committed, which included the use of rape as a weapon of war. To this day Mennonites that fled the Ukraine to the US are horrified by the name of Makhno and one of the main Mennonite museums in the US has a clock that had formerly placed on the wall of a Ukrainian Mennonite's house. Makhno, upon raiding the particular Mennonite village and plundering it for all of its wealth, had taken up residence temporarily in this house and, upon the clock chiming, he ripped it from the wall and stamped on it with his boot in his fury.

Here's the clock in question:

The Mennonites keep the clock as a reminder of the violence and destruction that Makhno and his forces inflicted upon the Mennonite community by persecuting them.

Makhnovia, rather than being proof of the fact that a stateless society is possible without a transitional state, proves the very opposite — it showed every semblance of engaging in most forms of creating a repressive state, besides its naive antipathy towards infrastructure which either would have destroyed Makhnovia from within or which would have required direct intervention to prevent this from occurring (through purges and liquidation, if not outright civil war if it was allowed to get that far), and it was not a triumph of anarchism but in fact a betrayal of anarchist principals. If anything, Makhnovia stands testament to the necessity of a transitional state to suppress counter-revolution and the suppression of rival movements.

Believe me, I know because I used to be an anarchist. It was in large part by my independent research into actually-existing anarchism that I lost faith in anarchism as a movement but especially in the anarchists who provided me with false historical narratives like these you're touting which were not backed up by anarchist historical accounts from first-hand witnesses (such as Volin and Arshinov) and from anarchist historians or historians sympathetic towards anarchism (such as Shubin, Malet, and Skirda.)

I can go all day discussing these matters.