I agree. I didn't see a clear question at all & love your phrasing of the goalposts being moved. And since I'm the one who could easily be perceived as being the "rude" one, please allow me to explain. Firstly, I am genuinely sorry if I came across that way. I'm not that person. I do come across very different in text where you don't see facial expressions or hear tone of voice and I sometimes forget that, so apologies there.
I was trying to offer ways to get the Kobo gift cards so OP could use them & be happily on their way. But I find it incredibly exasperating when people want everything served to them on a silver platter with little effort and for free.

Well, I'm sorry but life doesn't work that way. Sometimes you have to make sacrifices, ie paying the one time fee on a pre-paid card.
I am a large sized person with a twisted sense of humour, sarcastic, dry, deadpan, tongue in cheek and wordy etc. I remember as a younger person laughingly scoffing at One Size Fits All labels on clothes. I'm in the dressing room looking in the mirror with some garment stuck on my head laughing, thinking um, no, no, they're frigging not! Labels have since changed to One Size Fits Most. The moral being, not everything is right or suited for everyone. Pick the least inconvenient.
As Mick has said many times, you can't always get what you want. OP was not clear in their message and to me, seemed argumentative when presented with options. They had so many restrictions they cut themself off of any options available to them.
- prefers Kobo because they have the device but buying books presents problems
- doesn't have or want a credit card
- doesn't want a prepaid card because of fees & "difficulty" registering
- only wants to buy gift cards with cash to be able to buy ePub books for their Kobo
- doesn't want to use Calibre because they hate it & it's a "hassle" to convert (see other threads by them)
- doesn't want Amazon books because of above
Pick the lesser of the evils presented. If your preferred option for ease is Kobo gift cards & the Kobo bookstore, then spend $5 buy a $100 card and off you go. Happy life. Or look for one with no, or less fees for goodness sakes. No. Too much of a "hassle" to register. Yeesh!
But no, that's not good enough, I'm told essentially to pay his/her fees & register it for them. Fffft! If you box yourself into a corner and cut off all offers of help or solutions for whatever reason, you're going to be sitting in that corner for a long time.
*shrugs* I don't know what else to say.