TDE website:
https://www.trinitydesktop.org/
Arch Linux PKGBUILDs:
https://github.com/michael-manley/Trinity_ArchLinux_PKGBUILD
Inclusion of qt3 into repository is unlikely.
@Chocimier but there's a fork called tqt3 that's still maintained and used by this desktop environment. So you don't have to rely on an old and officially unsupported qt3.
Has this been assigned? I might take a look at it if not
@BenEvolent333 I don't think so.
I'm curious about this too so I'm going to see if I can get a build happening, will post here if it goes anywhere.
Status update:
I have the packages here up to tdebase building and running core applications with a few features turned off, you can check the current progress here.
I haven't tested running a full desktop environment yet, I'll report back if I do get that working & with more details on what I have and haven't gotten to work.
EDIT: TDE running via Xephyr with the following script:
#/bin/sh -e
SCREEN=800x600
NEW_DISPLAY=:1
Xephyr -br -ac -noreset -screen ${SCREEN} ${NEW_DISPLAY} &
PREFIX=/opt/trinity
export DISPLAY=${NEW_DISPLAY}
export PATH=${PREFIX}/bin:${PATH}
export LD_LIBRARY_PATH=${PREFIX}/lib:${LD_LIBRARY_PATH}
exec starttde
Screenshot bellow :)

Maybe I'll try to continue packaging that software to xbps. Also, the newer version of TDE has been released some time ago.
@kpvsky I'm late, but feel free to use my progress as a base. Iirc I left it because it's a lot of work to get everything else working and probably in a state that the core team would find acceptable, and the only member of the core team who was interested was Juan who is long gone.
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I'm curious about this too so I'm going to see if I can get a build happening, will post here if it goes anywhere.