I used the same private DNS address for my previous Samsung phone and it blocked off most ads across all apps.
Samsung probably has a built in blocker or something.
DNS blocking cannot block ads that originates from the same source and to block ads on youtube, it also may needs to do comestic filtering which network side cannot do
Are you browsing through the apps or using the browser?
if app, then there is no way any adblocker can block properly since it needs to detect things like this
Example - blocking youtube videos that list as UPCOMING
youtube[.]com##ytd-browse ytd-rich-item-renderer:has(ytd-thumbnail-overlay-time-status-renderer[overlay-style="UPCOMING"])
Example - blocking youtube videos that list as a live event or timed event that has "notify me"
youtube.com##ytd-rich-item-renderer:has(span.yt-core-attributed-string--white-space-no-wrap:has-text(Notify me))