In this thread the subject of different launchers is explored
There is one more thing you might try. /e/OS employs Trebuchet as well as Bliss (but Trebuchet is unusable as a launcher). It is hidden away as a system app; it might be worth clearing storage on that at the same time when you clear storage on Bliss;
Settings > Apps and notifications > See all … apps > 3 dot menu top right > Show system > Trebuchet > Storage & cache > Clear storage.
Edit. Reading your OP again, maybe worth mentioning that the weather widget is actually, as I understand it, “included” in Bliss. So the widget does not really have very much functionality, in that it is not “linked” to a specific weather app as one might assume.
As a “Weather App” I happen to use Forecastie. I do not find that the two conflict. I wonder if you installed any other Weather app which is causing a conflict with the widget / launcher ?