I did some more investigation on how to set the umask for the user session in systemd, but I couldn't work out how to do it. I tried adding
[Service]
UMask=0027
to ~/.config/systemd/user.conf, or to ~/.config/systemd/user/umask.conf, but with no effect. Searching online I couldn't find anything about precisely setting the umask of the user session. (In any case, this would only be a work-around, as the setting would still be duplicated from my .profile; what is really needed is a similar setting to that available in dbus.)
I did some more investigation on how to set the umask for the user session in systemd, but I couldn't work out how to do it. I tried adding
[Service]
UMask=0027
to ~/.config/ systemd/ user.conf, or to ~/.config/ systemd/ user/umask. conf, but with no effect. Searching online I couldn't find anything about precisely setting the umask of the user session. (In any case, this would only be a work-around, as the setting would still be duplicated from my .profile; what is really needed is a similar setting to that available in dbus.)