I've tested TDE with ExeGNU, Q4OS and PCLinuxOS recently and they all use a similar amount of RAM.

ExeGNU and PCLinuxOS use around 230-240MB and Q4OS uses ~260MB (didn't use swap on any of them). They all use Trinity DE and Trinity Windows Manager so they're pretty much identical. Only Q4OS uses systemd.

Is it possible that it's a new install and maybe you installed other programs which were running on the other distros? Fotoxx could rely on some non-free service or something that's not present in Devuan but that's just a guess. Strange.

Also I've discovered ExeGNU very recently and the next day while searching for it I found your article, it was helpful and I found this forum so thanks for that davidb. I think its a very usable truly free/open distribution and wonder why it has so little coverage.

Just in case you don't know there is an email to contact the developer info@exegnulinux.net which is listed on the sourceforge site you could try that. There is a 32bit beowulf iso under testing so I don't know why there hasn't been a new release.