I have just updated my game to the 1.5.10 version with all expansions. I am playing offline without the online features.
All donator features like exploration mode, possessor class etc are locked to me. Previously there wasn't a problem with that. I adn't need any account or registration before.

Are you on Windows? If yes, then https://www.gog.com/forum/tales_of_majeyal/possessor_bonus_class_disabled_in_1510_linux_version is not an Linux installer issue.

Yes I am on windows 10

I can confirm this issue as well.

Also, I am now getting constant pop-up's that nag for an "automatic monthly recurring donation".
( AKA paid subscription )

These issues also effect people who "donated" at te4.org, even after they connect online to their te4.org account.
Same problems, using the GOG or te4.org version.

I tested the following versions : ( game v1.5.10 )
te4.org ( Windows / Linux32 / Linux64 )
GOG ( Windows / Linux )

This is a really sneaky way of pushing DRM onto a paying customer.

*edit*

Ditto. Fully offline, airgapped Windows 7 64bit PC, Uninstalling 1.5.10 and installing 1.5.9 restores donor status but then you're on an old version.

I've just noticed that there are authentication keys available for download here at GoG, but I don't see where to enter them in the game. Maybe they're useful for creating an account at the game's website?

Anyone can create an account on te4.org. The keys give you donator status/access to the DLC's.

Can confirm this problem as well. Very annoying, especially since I can't tell whether it's intentional or really a bug.

ToME is free software with donator benefits by design, full stop. You get more item vault slots if you donate more, plus the currency for new DLC releases (if you plan on buying only GOG items, you don't care about the latter). What GOG and Steam sells is the version available to dnators. If you take a look at how the site sells the game, you'll understand a bit more. https://te4.org/donate

Now, whether you can call that DRM or donationware is up to debate. I don't really know if it's even possible to get rid of the donation notices for certain builds or by addon. There's an option that turns off all online features, but you're shutting yourself out of a pretty good list of things (the option description lines out a lot). It's more for the free players.

That was there previously, and annoying but easy to ignore, but what's changed between 1.5.9 and 1.5.10 is that the donator features such as the Possessor class, extra cosmetic options and explorer mode no longer work playing offline as they did previously. Hopefully this is a bug or an oversight as this is more than a little aggravating.

That I can tell you at least isn't GOG specific. I'm running the version from the main site's downloads, and I've run into this with Exploration mode while the server was fluxuating (apparently they're working on a way to fix this in later versions, the fault is the heavy load). I was a bit weirded out to say the least, because my sheet was marked Exploration after a fun run.

Here's hoping something is done about it either way.

Of course it is GOG specific, as the offline mode with donator features is something that is exclusive to GOG's version. Or at least it used to be as it is now completely broken in 1.5.10.

Any news about the problem?
DRM free is DRM free...I DON'T WANT TO BE FORCED TO CREATE AN ACCOUNT SOMEWHERE TO USE THINGS I BOUGHT!
FIX THE OFFLINE MODE!

I just purchased the game on GOG after enjoying it for free from te4.org, in the hopes it would unlock the donor perks.
I gather that I need to enter my product key at te4.org/key-redeem after searching these forums, but I cannot seem to find a product key anywhere?

Am I looking in the wrong places? Does purchase on GOG not include donor-perks?
I'm so confused with this whole process.

I don't really care about playing online vs offline, I just want to check out the extra donor content I thought I was paying for.