I do not want to update my game to 1.6 yet, but the DLCs available are only for 1.6. How can I get the DLCs that match my game.??

You can't download older version on the official website and the library on GOG. You could try to use Galaxy (or Steam) to roll back to the previous version. That would probably work.

Thanks. I tried to get the 1.5 DLCs by installing 1.6 versions and rolling back. I'm not sure if I ended up with a correct install. Please let me know if this is how it's supposed to look? At the the new game Char Creation page, I can choose "Orcs: Embers of Rage" or "Age of Ascendancy." What about Forbidden Cults and Ashes of Urh'Rok? If I choose Embers, only Orc race and warrior and tinker classes are available?

Thanks for any help, and if there is a doc or info somewhere on this stuff... where?

Forbidden Cults and Ashes of Urh'Rok don't have separate campaigns. They are a part of "Age of Ascendancy." The other races/classes are unlocked by reaching certain ingame places/situations. There is a page of spoilers on the ToME wiki: https://te4.org/wiki/Unlockables

If I might ask a grain of curiosity, why are you staying on 1.5?

I'm pretty new to Tome, and liked what I was finding with 1.5.1. Trying to stay spoiler free, but reading experienced players' reactions to 1.6 gave a picture of too many changes, too many big changes, fixes for things that weren't problems, and not really ready for prime time release. Admittedly just a feeling. But 1.5 is very good so I'd just like to go further with it. I'm looking forward to buying into the new release at some point after it matures a bit. It's already up to 1.6.4 so we'll see.