Vivaldi with uBlock Origin here. A simple refresh of the page makes the popup go away, often for the rest of the session. For me, it's YT without ads as usual. I might need to clear uBlock cache and refresh filter lists to make it work even better. There's also a Tampermonkey script for blocking the popup, but I haven't tried it yet.
As a side note, I've seen a lot of talk about boycotting Youtube. There are 3 things to consider with this:
Boycotting YT will give Google exactly what they want, getting rid of the "freeloaders" who don't pay for Premium and block ads.
Boycotting YT will hurt small creators who don't see much ad revenue (if any) anyway. Views and likes are what make small creators visible to the algorithm, if these drop off, their reach will diminish.
Boycotting YT won't affect big creators with sponsorships, healthy Patreon community, millions of subscribers and views.
Best way of defiance here is not stopping to use YT, but on the contrary, generating as much traffick to YT as possible while blocking the ads.