There's an error in the current "mullvad-vpn-dinit" file, available from the aur.
Here's the package that will install:
type = process
command = "/usr/bin/mullvad-daemon" -v --disable-stdout-timestamps
smooth-recovery = true
logfile = /var/log/dinit/mullvad-vpn.log
waits-for = loginready
If you use this you'll get errors because dinit doesn't recognise "loginready"
So, you can either remove (comment out) the line "waits-for = loginready" or, if it's helpful to other Mullvad VPN users, here's my dinit service file for "mullvad-vpn-cli".
type = process
command = "/usr/bin/mullvad-daemon" -v --disable-stdout-timestamps
smooth-recovery = true
logfile = /var/log/dinit/mullvad-vpn.log
before = login.target
depends-on = network.target
God bless. That was exactly the hitch I had last night upgrading after coming back home from a trip, and the solution at the end is what helped me out. I think simply removing the waits-for line was still causing problems and preventing normal boot.