I haven't been able to pay GOG via PayPal for 2-3 months on Opera, Opera GX and Vivaldi browsers—all Chromium-based, ie same engine as Google's Chrome browser.

Anyone else having recent good/bad PayPal experience with any of my browsers?

Not a big deal as I can pay by card, but I prefer PayPal when possible.

Never been a issue for me using Vivaldi and PayPal, worked fine a few days ago. There might be an browser extension/addon that blocks PayPal because it will popup a new window. You can also check you firewall if it might be too aggressive on blocking stuff such as popups that some firewalls block as well as other stuff.

Other than that you can try paying through the GOG Galaxy client, it might work better.

Have no problem on Google Chrome dev for recent months, including this Winter Sale.

Weeks ago I encountered an PayPal glitch but it was 100% PayPal's fault.