Sorry about that!
I definitely know what caused this problem with Elisa, basically I was too broad with the matching rules (I matched everything KDE which is obviously dumb). As best I can tell, it seems like it’s safe to just remove the line mentioned above, and everything should still be covered by other match criteria.
On a similar note, I also noticed that this could mess with the volume meters for certain devices, so I’ve added a couple of lines to make sure we exclude those.
I also fixed a typo that I don’t think is causing any issue but while I’m doing version 0.2 … 
Give that a shot, I expect it should work, but if you have a problem with an app being matched as a Notification like this, or vice versa, if you have an actual Notification which is not matched, let me know, and I’ll work on the rules.
Since I can’t edit the above post, posting the updated code here:
~/.config/pipewire/pipewire.conf.d/60-notifications-volume.conf:
# Notifications volume
context.modules = [
{ name = libpipewire-module-loopback args = {
capture.props = {
media.class = Audio/Sink
media.name = "Notifications"
node.name = "Notifications"
node.nick = "Notifications"
node.description = "Notifications"
node.passive = true
node.virtual = false # Special treatment to always show this in volume control
}
playback.props = {
node.name = "Notifications"
node.description = "Notifications"
node.linger = true
node.passive = true
channelmix.disable = true
channelmix.min-volume = 0.0 # Alter these if required
channelmix.max-volume = 0.60 # Volume will be clamped to these levels
} } }
]
node.rules = [
# System notifications
{ matches = [ { media.role = "Notification"
} { application.id = "org.freedesktop.libcanberra"
media.role = "!Test"
application.process.binary = "!systemsettings"
} { application.name = "libcanberra"
media.role = "!Test"
application.process.binary = "!systemsettings"
} { application.process.binary = "plasmashell"
media.name = "!PlasmaPA-VolumeMeter"
node.rate = "!1/25"
} { application.name = "konsole"
} ] actions = { update-props = {
target.object = "Notifications"
} } }
]