Prior to 1873 - they did not have to pay ANY taxes in exchange for the military service that was required?
After 1873, who did the taxes go to? Was it to the AH government or the wealthy land owners?
How did a farmer even make money to pay the taxes? Since they no longer had wages from their military service, where did they get money from?
As a rule, all conscripts between the ages of 16 and 60 served as Grenzer in the army. During the peace they made their living from agriculture and trade. It turned out, however, that the military border has many problems to get the basics for the population. There was always famine. Either because of the war or simply because the populated areas were unfortunately only partially unified for agriculture.
Because of the repeated famine, there were several attempts to carry out fundamental reforms in the area of the military border. Above all, this meant subordinating the administration of the military border to civil administration. Croatian and Hungarian nobles, as well as the Catholic Church, campaigned for this right from the start. All these reforms failed, but the border guards' privileges were successively reduced. This means that even before 1873 some privileges were only available on paper, while in reality other rules applied. In this sense, the Grenzer had to adjust and tried more and more in trade or settled in other areas where it was easier to do agriculture.
After the military border was officially abolished, this led to a wave of emigration within the monarchy and even more often to North America. In 1873 the generalates of Warasdin and Karlstadt were finally incorporated into the civil administration of the monarchy and that meant the population had given their taxes to the civil administration of the Austro-Hungarian monarchy and not to the nobles.
It should be emphasized that not all Orthodox were automatically conscripted and tax-free. There were also classic peasant families who worked in agriculture and were subject to taxation even before 1873. They paid their tax (tenth) to the aristocracy and the Catholic Church. The clear majority, however, was tax-free.
I hope my answers could help you a bit.
Best Regards