Reviving an old topic : if you, like me are using "dark reader" and have some troubles with the new gmail style, just open the settings for "dark reader", click on "More...", then choose either "Filter" or "Filter+" for gmail, but then don't forget to remove the news below (x), and then choose "for this site only", because most other sites work fine with the dynamic setting, but the icons of gmail at the top of the screen become invisible if using dynamic.
That's all, and the "dark" themes from gmail without "dark reader" leave the background of the mails in white, so they are nice but not really useful, but you can combine them with dark reader by using this setting !
Thanks again to mer-curious for finding this extension !