Lets try to answer some of the theme issues being raised around various forums.
GNOME 42 brings libadwaita and the enforced dark & light styling using just libadwaita colours - i.e. you cannot use your own GTK Theme. Anything else you may read in this area is a hack. Fortunately only a few apps in 22.04 are libadwaita based … but you will see many more in 22.10.
Also - libhandy based apps similarly have this dark & light styling … but it only recognises the users dark or light GTK+3 theme if the theme name ends “-dark” or “-light”. Its hard-coded. So unlucky if you are using a theme that has dark or light in the middle of its name or is “Dark” rather than “dark”.
In addition - you need to tweak a gsettings key to set your preferred dark or light style for these libhandy/libadwaita apps - easier to use dconf-editor and navigate to org.gnome.desktop.interface.color-scheme and change the value there.
Snaps now can inherit your user based theme … but only if the theme has been published as a snap in the snap store… and if the author of the snap has asked for permission to allow autoconnections.
The ubuntu budgie team has done this for Pocillo and QogirBudgie. Any other theme you need to ask nicely either the theme maintainer to-do … or if they don’t want to, go through the process yourself … or ask nicely a willing snap packager.