A popup that tells people to install an ad blocker

A simple one from https://sciops.net/

<div class="ftf-dma-note d-none ad native-ad native-ad-1 ytd-j yxd-j yxd-jd aff-content-col aff-inner-col aff-item-list ark-ad-message inplayer-ad inplayer_banners in_stream_banner trafficjunky-float-right dbanner preroll-blocker happy-inside-player blocker-notice blocker-overlay exo-horizontal ave-pl bottom-hor-block brs-block advboxemb wgAdBlockMessage glx-watermark-container overlay-advertising-new header-menu-bottom-ads rkads mdp-deblocker-wrapper amp-ad-inner imggif bloc-pub bloc-pub2 hor_banner aan_fake aan_fake__video-units rps_player_ads fints-block__row full-ave-pl full-bns-block vertbars video-brs player-bns-block wps-player__happy-inside gallery-bns-bl stream-item-widget adsbyrunactive happy-under-player adde_modal_detector adde_modal-overlay ninja-recommend-block aoa_overlay message" style="color: white; background-color: red; padding: 1em; text-align: center; border: 1px solid white; margin: 1em auto;"> <p>
WARNING:  you do not appear to be running an ad blocker!  <a href="https://ublockorigin.com" style="text-decoration: underline"> Click here to install one immediately</a>.
</p></div>

A much fancier one from: @rustydev

https://codeberg.org/rustydev/anti-ad-nag/

https://codeberg.org/rustydev/anti-ad-nag/raw/branch/main/index.html