Apparently refreshing is not possible, so upgrading is not possible. First I removed all trinity packages.
From https://wiki.trinitydesktop.org/Mageia_Trinity_Repository_Installation_Instr... these are in my script: # urpmi.removemedia trinity trinity-noarch # urpmi.addmedia trinity http://mirror.ppa.trinitydesktop.org/trinity/rpm/mga8/trinity-r14/RPMS/x86_6... # urpmi.addmedia trinity-noarch http://mirror.ppa.trinitydesktop.org/trinity/rpm/mga8/trinity-r14/RPMS/noarc...
Running script with 2>somefile produces: trying to select nonexistent medium "trinity" trying to select nonexistent medium "trinity-noarch" invalid MD5SUM file (downloaded from http://mirror.ppa.trinitydesktop.org/trinity/rpm/mga8/trinity-r14/RPMS/x86_6...) invalid MD5SUM file (downloaded from http://mirror.ppa.trinitydesktop.org/trinity/rpm/mga8/trinity-r14/RPMS/noarc...)
Using trinity/trinity/ in the URLs as was the configuration for Mageia 7 instead of just trinity/ didn't help. Doing same but with tde-mirror.yosemite.net instead of mirror.ppa.trinitydesktop.org eliminated the error, and
urpmi trinity-tdm trinity-tdebase
succeeded to produce a working TDM and TDE session.