View the site in Reader view (click on the “AA” in the lower left of the screen). It removes everything but the text of the site, including ads, blockers, almost all membership requests, etc.

Edit: Reader view is not available for that site, so my suggestion won’t help in this case.

Try going into the AdBlock settings and turning on an "annoyances" filter. uBlock has these built in, but they aren't active by default.

I am using 1Blocker and did not get that popup from that site.

What extensions are you running?

I've been using Adguard for years and seems to be working well.

I don't see it, but then I'm using 3 different things that might stop it (adguard and stopthemadness extensions + nextdns dns).

Most adblockers have a filter for anti-adblock, I think under Annoyances. I use Aha DNS Blitz on my phone. Any reputable blocker (ublock, adguard, etc.) should have that filter.