1. I went to apt.pearsoncomputing.net/cdimages/index_desktop.html, got the Kubuntu 10.10 Maverick (Intel x86) ISO image, installed it from CD, then added some favorite packages.
2. Installed and ran update-manager. It upgraded all the non-KDE packages to Natty. Rebooted, and everything still works fine.

When trying to go further, problems arise:
A. I made sure that sources.list had no references to KDE or Trinity. Ran update-manager again to upgrade to Oneiric. It stopped with the message "An unresolvable problem occurred while calculating the upgrade: The package 'kubuntu-desktop-kde3' is marked for removal but it is in the removal blacklist." So nothing changed.
B. In sources.list added the four Maverick lines from www.trinitydesktop.org/installation.php. After updating the repositories, Synaptic offers to do a lot of *-kde3 upgrades and *-trinity package installs. But I don't dare, not knowing what will happen.
Because last week I did the same steps 1 and 2 above, then added the Natty repositories to sources.list, then blithely did update/upgrade - and rendered the whole installation unusable!

So I wonder how to get to using the current Trinity desktop. Does it require a different approach? Like installing a current Debian or Lubuntu desktop, then adding the relevant Trinity repositories, then installing Trinity core packages and making tdm the default desktop manager?

I have no idea, but I used Trinity until last year, and they have an extremely friendly and helpful mailing list. The current person in charge of Trinity development/maintenance is always present and dispenses a lot of accurate and useful advice. I think you should subscribe to it, even if temporarily, and get all the help you need.

One problem with Trinity is that it now sort of kind of lives in its own world, since all distros only take KDE4 into consideration. Even if one or the other distro carries Trinity (KDE 3.5.x) in the official repository, you're bound to run into problems occasionally because the distro really wants to assume KDE4 on every other opportunity.

Thanks, I just subscribed.

I wonder what it would take to launch a Trinity distro...

Perhaps if you installed Trinity on a distro that didn't customise software, like Slackware or Debian(?), there might be fewer problems. Also, switching from KDE to Trinity may give more trouble (as you've found) than switching from something else or nothing at all. If I were doing it, I think I'd do a minimal Salix installation, add Trinity's Slackware package, and then install the applications from Salix: slow but sure.

Thanks for the replies.
In the Trinity mailing list's November archive I learned of Exe GNU/Linux, with a link at http://exe-linux.fastfishwebsolutions.com/tde to a tde3.5.13 image. Will try it out.

28 January - installed Exe GNU/Linux from USB drive. It ran, but I had a lot of trouble becoming root to install packages and configuring internet access.
Replaced it with Lubuntu 11.10, installed also from USB. Runs fine, including internet access. After updating it I added the Oneiric repositories per www.trinitydesktop.org/installation.php, installed Trinity desktop and packages, set TDM as the default desktop ... so far looks like it works fine!

I recon this would be the way to go. most other distros aren't as hard as some Ubuntu users will have you believe either. I'd suggest Debian; i believe they have it in there repositories. I don't know how well trinity and kde play with each other, so you may want to go with the gnome or xfce desktop initially, or alternatively install no gui and then install xorg and trinity later. I've done this except with twm instead of trinity and it is very easy, just two simple apt-get's