Opera's "startpage" now takes a very long time to get through

Windows 10 Pro.

When the first instance of Opera is started, then trying to access any URL first goes to "opera://startpage/" address and then jumps to the actual URL

Screenshot (768).png

Normally, the "opera://startpage/" stage ends very quickly. However, since around February 10 this stage began to take surprisingly long time. In my case Opera spins, spins and spins in that "opera://startpage/" state for about 10 seconds or more and only then proceeds to the actual URL.

If I globally disable AdGuard, everything returns to normal. This intermediate stage flashes through quickly. But re-enable AdGuard again and it becomes slow again: 8-15 seconds doing something with that "opera://startpage/".

Again, this wasn't a problem before. It just started relatively recently sometime around February 10.

Is there something I can do to alleviate this annoying issue?