That's not the problem for me. My book sell one copy every 3 month, with Amazon I get the money, with kobo I would need to wait to reach 50$ (and my ebook cost 3,26€ and I get 70% of that - 4% of taxes (only because it's a book usually vat is 22%).
I'm still trying to solve the problem with Amazon, if I cannot I'll link a itch widget for those who want a drm free copy instead.. That way I can get the money for each transaction and sell a drm free copy at the same time.

Still if you got a Kindle e ink you can still access to the drm free copy, just use the transfer USB function on your account, the problem right now is for people that don't own a kindle since the website do not allow to transfer usb if you don't register a Kindle and you cannot get a drm free copy from mobile and desktop app (at least not officially, you can still disable the KFX support on the desktop app).
So I'll write this on the description of my ebook with the link to a itch widget to buy the game externally and get a drm free copy if it's not possible to get a drm free copy on Amazon for them.

I still wrote to Amazon to solve this problem. Right now their answer where not good at all. Still there is still a possibility that they will solve the problem.

I also want to try to just upload my file instead of make them convert a doc file... The reason for this is that my manga still use the old format and I read that KFX should be compatible with manga. I think the reason for this is that they upload a file converted from epub generated with kindle previewer. I will need to try it in the near future.

As a customer I'll start to use kobo more, but for book with drm there is no real difference, if kobo start to use ADE 3+ instead of 2 the plugin to remove drm will still not be able to remove the drm.
Once each of them fail to remove the drm I'll just stop to buy ebook from both store until there is again a solution to remove the drm.
We will see if that day will come.

Ps. I finally understand why everything changed on the last few weeks.. From 1 August 2021 they don't allow mobi anymore for kindle ebook with a not fixed layout (so Manga that use a fixed layout still got the mobi format that's why I got drm free manga from kindle pc app). It also still download a Mobi file from the transfer USB amazon website and on old e ink device. So I asked to the support the instructions to get my ebook in the static format that accept mobi.

Amazon support was not helpfull at all.
In the end I didn't even used itch because I decided that my customers deserved to get an even better service.
I just put a dropbox link in the description with the download for the drm-free version of the ebook with the explaination on how to get the drm-free version from amazon with a kindle and an explaination on how you can get the book legally from that link only if you bought it before.
I think drm-free is about trusting your customers in the first place so if I have to trust them there is no reason to make it to much complicated, if they really want to support my ebook they will just buy the ebook anyway, if they don't they will pirate it even without a link.

And I am not surprised.
While it can be helpful sometimes, it depends on who you deal with, especially if not from the right USA timezone.
I always try to elevate any issue I have had, up the chain of command, so I get proper help ... usually.

Have you checked out Smashwords?
Sure it can be a bit like Itch.io for games, so overwhelming sometimes. But many authors, not just Indie ones, also sell a few ebooks via them.
I use it now and then, for some authors I follow, plus a brother-in-law has published many of his books and stories there.
Many ebooks sold at Kobo originate at Smashwords. You see that in many of the filenames of the DRM-Free ones you can download from Kobo.

- I just contacted them on amazon com instead of it and asked to send a bug report for the PC app. The reality is that when they introduced the new format (mandatory for ebook, not mandatory for comics and other fixed format) they "forgot" to implement the drm-free download for the KFX format (I tried, the format can be drm-free, you can generate a drm-free KFX file with kindle previewer, convert it to epub and even read it on calibre).
The reason why the ebook is still drm-free if you download it from the website and old kindle is that it will download a mobi file (the old format).
Mobi is mandatory from 1 August 2021 (this year) so I think it can actually be a bug.
If it's not a bug DRM-free is only possible right now for those who got a e ink kindle device.
Still I think it does not make sense that it ask you if you want drm or not when you publish an ebook and it just ignore it on the Kindle PC app (the only app that download a file if you don't have an e ink kindle device at least without workaround).

- I see no reason to use Smashwords instead of direct publish on the website supported by Smashwords. They will keep a fee, the minimum payout will not change. And you still need to deal with each website.
If I wanted to publish it on my own website (that I don't have) I would just used itch widget (that can be used for ebook too).
Since I just wanted to give a drm-free copy to anyone I just put a dropbox link in the description and I also said that you can legally use it only if you buy the digital or printed book. I trust my customers so there is no reason to make it complicate, people will get the amazon copy and they will also get a backup drm-free copy from me with a simple link in the book description (they don't even need to contact me).

I can understand that you are trying to convince me to publish the ebook also in another store but I don't really see another store with no minimum payout.

Reviving this thread again because I found this post that I feel like it's pertinent here, since Groupees sells DRM free ebooks every now and then:
https://www.reddit.com/r/GameDealsMeta/comments/rcny0t/groupees_is_undergoing_some_major_changes/

tl;dr: Groupees is doing some changes in 2022 and there's a chance DRM free contents you can download from your library may be at some form of risk (either retroactively adding DRM, removing the downloads or something else, it's not made clear).

Still, as the post says and as people should always do with DRM free contents they buy, back them up as soon as possible.

Heads up: I was doing some digging, and it seems that the Monogatari bundle from Humble Bundle is the only place where people can get the DRM free version of those titles, and the bundle will expire in a bit over 5 days.

Also is this an interesting use for this thread, to give warnings like those?

Yay, necro! But I think it's worth noting anyways:

As far as I know, the only place where Scott Pilgrim Color Collection was available DRM free was in the now-defunct Comixology. And now, the first two volumes (from three total, if I'm not mistaken) are available in a comic bundle from Humble Bundle.
I imagine (or at least hope) that the publisher is saving the 3rd volume for a future bundle, but if people want to secure what's available in the bundle, as well as giving a message that a DRM free comic can profit (and thus making it more likely for the 3rd volume to be available DRM free again), I think it's an interesting bundle to support. And besides, charity and the bundle is proportionally pretty cheap, with each volume costing ~0.50 USD.

Another necro, but it's worth it, as it would seem I found another resource:
All purchasable comics in the erotic store Fakku appear to have a DRM free ebook option when purchasing (put the title in the cart to see the purchase options).
Just mind you can't download the titles from their subscription service, and I have no clue if there are titles exclusive to their subscription service, and their search system isn't really helping.

Reviving this thread since someone mentioned in another post something pertinent to here, a store called "Vault Comics" which was supposedly selling DRM free comics. Upon testing, it does seem to be the case. To test, I purchased some random comic there, and it was delivered as both PDF and EPUB in my account.