One of my installs has this odd “orphan” thing too. Although my orphan list is not quite as extensive, it does have quite a few packages that I know I installed.
pacman -Qtdq
bluetooth-autoconnect
dconf-editor
eog
ethtool
firedragon
firefox
garuda-settings-manager
geocode-glib
intel-ucode
js78
kfiredragonhelper
lib32-readline
libcddb
libibus
libvisual
libxnvctrl
micro
neard
networkmanager-support
ntp
python-beaker
python-nspektr
rest
ruby-dbus
signal-desktop
t1lib
usbip
vivaldi
xdg-user-dirs
xf86-video-intel
Signal and Vivaldi browser are especially odd to see on this list; not only did I explicitly install them, but what other package could possibly be using these as a dependency?
The only thing I can think of is the Setup Assistant post-install wizard could play a role somehow, because I often use that tool to install my browsers and Signal. That’s only a shot in the dark though, I’m really not sure. 
This isn’t the first time this has come up; Technetium had a thread over the summer where he had tons of packages this was happening to:
This command does work perfectly fine to get packages off the list, and marked as explicitly installed:
It is not always clear if a false orphan should be kept or not, however. The significance of some of the libraries are often not obvious, for example. And how did ntp end up an orphan? Nothing needs that?! 