Session Mismatch on every login

[nhlpl]

A window/screen posted here (Session Mismatch, see below) can be seen on both community.nodebb.org and try.nodebb.org.
#7050 (comment)

Happens for all newly created accounts and old one. I can see it just after successful login. For a second or two and it disappears. No need to close it or click anything.

Chrome-based Opera browsers (Windows) with built-in ad-blocking/privacy tracker (Opera based, preinstalled). It helps when such software is being disabled. Also works fine on Chrome 84.0.4147.135 where no extensions are installed.

Not a bug but most people use such software or enable such feature in their browsers. It would be good idea to check for ad-blockers or change it in some other way.