In Opera: right click anywhere. Select Block Content. Click on any annoying banner ads which tries to find a block pattern. No default filter like AdBlock, but pretty easy and a core element of the browser.

I'm an Opera user on Linux because I found it somewhat faster than Firefox back N years ago but I'm not sure I'm hanging on to Opera out of anything but loyalty and stubborness. Both Opera and Firefox (which is better at handling Gmail) bloat up to awful amounts of memory with time (why is Opera using 400 megabyte RSS now after 3 days?))