indeed, i just got the exact same error log; here it is:

error: failed to commit transaction (conflicting files)
psmisc: /usr/share/man/de/man1/fuser.1.gz exists in filesystem (owned by man-pages-de)
psmisc: /usr/share/man/de/man1/killall.1.gz exists in filesystem (owned by man-pages-de)
psmisc: /usr/share/man/de/man1/peekfd.1.gz exists in filesystem (owned by man-pages-de)
psmisc: /usr/share/man/de/man1/prtstat.1.gz exists in filesystem (owned by man-pages-de)
psmisc: /usr/share/man/de/man1/pslog.1.gz exists in filesystem (owned by man-pages-de)
psmisc: /usr/share/man/de/man1/pstree.1.gz exists in filesystem (owned by man-pages-de)
Errors occurred, no packages were upgraded.

`pacman -Ss psmisc`
core/psmisc 23.4-1 [installed: 23.3-4]
Miscellaneous procfs tools

i doubt that it is a user introduced error as i just installed arch afresh a few days ago
and did not install or otherwise put much on the system. there are exclusively pacages
from the offical arch repos. no aur, no compiled source code.

`uname -a`
Linux <pcname> 5.10.13-arch1-2 #1 SMP PREEMPT Sat, 06 Feb 2021 11:07:29 +0000 x86_64 GNU/Linux

same here, fresh install, no tweaks

Same error here. There seems to be an upstream fix already according to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982059 but that seems to be only a partial fix.
Are there any workarounds though? This breaks updates in general.

You could update everything except psmisc. Or uninstall man-pages-de for the time being. That's what I did when narrowing down the issue: https://0x0.st/-H6o.txt

I went with the second option - no partial updates ;)

all you need to do to get it working for now is to remove the files the error message lists and run the update again

uninstall man-pages-de
install psmisc
install man-pages-de

worked for me

@midixinga – that's interesting/strange since I had uninstalled man-pages-de to be able to do a proper pacman -Suy, yet as I tried to install man-pages-de just now, I still got the same error as in the original post (except for "owned by psmisc", as shown in my pastebin above).

If the order of events is (1) psmisc and man-pages-de are installed (2) update of psmisc shows conflicts, then deleting these 6 files indeed seems to be the best option.

If you (1) uninstalled man-pages-de to be able to (2) do a full update including psmisc, then that deleting the 6 files is not a good idea. Reason is that the new ones (dated 2020) would be deleted and "replaced" by the old ones (dated 2016) when (re)installing man-pages-de. The new man pages do contain new program options and corrections.

If you build man-pages-* from the attached source bundle, which is a simple version update to 4.9.2 are all the file conflicts resolved?
Have any new issues been introduced?

So I'm to late to be the first one reporting that "[psmisc] 23.4-1 from core conflicts with man-pages-de 4.2.0-1 from community".
Folks, this is a bug tracker. Everybody using Arch Linux should be aware how to workaround this issue, if not, there are appropriate forums to request help.
It makes no sense to mention the age of an Arch Linux install.

Updated man-pages-l10n to version 4.9.2-1... Should be fixed now, no?

man-pages-l10n 4.9.2-1 (in my case: man-pages-de 4.9.2-1) fixes the issue for me.