I observed the same behaviour with my Firefox 126.96.36.199 but only when using dotln-master as the default template: it works ok with theme-selva and so I selectively apply theme-selva to the adp pages where I want to use Xinha.
If I comment the line 315 of the next file:
/*float: left; */
work Ok with Firefox. All appears right and I have no
detected secondary effects (yet ).