We need to find which property is applying the blur (Maybe it is in your theme, or an obsidian default). Use the inspector to check where the blur is being applied:
Another guess:
.theme-light .workspace {
backdrop-filter: none!important;
background-color: transparent;
}
.theme-dark .workspace {
backdrop-filter: none!important;
background-color: transparent;
}
body {
--background-primary: transparent;
--background-secondary: transparent;
}