Not all packages references have been adapted to the new version yet.
You can tell your system to user the previeous release.
But don’t forget to set it back to the correct one afterwards.
I don’t know it it’s perfectly correct (working till yet) but what I did yesterday in the same case was:
I a terminal, as root:
ssu re 4.3.0.12
zypper ref
Install Storeman, then again as root:
ssu re 4.3.0.15
zypper ref
If you havent installed zypper yet, you can, as root with:
ssu re 4.3.0.15
pkcon update
pkcon install zypper
zypper ref
Maybe simpler, you could also download Storeman with, as regular user (defaultuser):
/usr/bin/sailfish-browser https://repo.sailfishos.org/obs/home:/mentaljam/
You’ll have to choose the version for your device.