Invalid AUR key updating darktable

I am trying to update darktable and having an error that appears to be from an invalid key.
I have used the Manjaro help page to flush and reinstall all keys but the problem persists. See the following:

[david@david-g5 ~]$ sudo pacman -Syu
error: graphics_darktable_master_Arch: signature from "graphics:darktable OBS Project <graphics:darktable@build.opensuse.org>" is unknown trust
:: Synchronizing package databases...
 graphics_darktable_master_Arch.db failed to download
error: failed retrieving file 'graphics_darktable_master_Arch.db' from download.opensuse.org : The requested URL returned error: 404
error: failed to synchronize all databases (failed to retrieve some files)

Help would be appreciated.


Moderator edit: In the future, please use proper formatting: [HowTo] Post command output and file content as formatted text

This isn’t even AUR. Custom repos aren’t supported. darktable is in Manjaro repos.

The error message that appears when I try to install any AUR program is “invalid or corrupted database”, so it looks like it is not a key problem at all.
How do I find something lurking in the database that could be causing the problem.
Now finding that this same error is shown when I try to install any software … so not just from AUR

Looks like the Arch project key key is my problem …

[david@david-g5 ~]$ pamac update --force-refresh
Preparing...
==== AUTHENTICATING FOR org.manjaro.pamac.commit ====
Authentication is required to install, update, or remove packages
Authenticating as: David Vincent-Jones,,none,6046038480 (david)
Password: 
==== AUTHENTICATION COMPLETE ====
Synchronizing package databases...
Error: graphics_darktable_master_Arch: signature from "graphics:darktable OBS Project <graphics:darktable@build.opensuse.org>" is unknown trust
https://download.opensuse.org/repositories/graphics:/darktable:/master/Arch/x86_64/graphics_darktable_master_Arch.db: Error 404
Error: graphics_darktable_master_Arch.db: graphics_darktable_master_Arch: signature from "graphics:darktable OBS Project <graphics:darktable@build.opensuse.org>" is unknown trust
https://download.opensuse.org/repositories/graphics:/darktable:/master/Arch/x86_64/graphics_darktable_master_Arch.files: Error 404
Failed to synchronize databases
Nothing to do.
Transaction successfully finished.

How should I correct this key?


Moderator edit: In the future, please use proper formatting: [HowTo] Post command output and file content as formatted text

No, using a third-party repo for no apparent reason is your problem. As mentioned above third-party repos are not supported. Remove it from your /etc/pacman.conf the same way you added it and install darktable from the official repositories using Add/Remove Software (aka Pamac) or:

sudo pacman -Syu darktable