I’m trying to understand the difference between zypper lu and zypper lu --all and what the dependency issues are with the packages
From
man zypper
list-updates (lu) [options]
List available updates.
This command will list only installable updates, i.e. updates which have no dependency problems, or which do not change package vendor. This list is what the update command will propose to install. To list all packages for which newer version are available, use --all option.
In other words: packages that have a newer version but require a vendor change when they would be installed are not listed. They are also not installed with
zypper up
for the same reason: you decided to install from a certain vendor and the system will not change that against your decisision.
What the dependency problems are in a certain case depends on the case. (When you have one you do not understand why, please start a thread about it which shows the command and the output, thus people can help you interpreting it)
I don’t actually get a dependency issue, zypper dup doesn’t see the update, neither does adding the --allow-vendor-change option. According to the man page this can be caused by either a change of vendor or a dependency issue. I know I’m on the vendor with the update so it must be the dependency unless I’m completely misreading the man page. I’m trying to find out how to find out what the dependency issue could be.
It’s more idle curiosity than anything serious though.
As you are using TW, you will not use zypper up at all. Only zypper dup. And then zypper lu is rather useless, because it shows what zypper up will do.