Installing Lightroom 6 for Windows: what is going on?

(Originally posted in 'Lightroom Classic' community, but this one is apparently more appropriate)

(First and foremost, this is not about downloading. I already have a previously-downloaded copy of Lightroom 6 installer.)

Lightroom 6 installer successfully unpacks itself and begins setup. However at the very start it produces the following screen

The link (and the QR code) leads to a web page, which wants me to sugn in using my Adobe ID. It asks me to enter my registered email and then states that a verification code has been sent to that email address.

However, the code never arrives. I made several attempts, nothing was sent to my email address.

So, what exactly is going on here? I understand that Lightroom 6 is out-of-support, but I don't care about support. What's more important is why there is still an active sign-in server, which pretends to send verification codes, when in reality nothing is being sent? And, even more importantly, how do I work around this. I would like to have Lightroom 6 installed on my machine.

Thank you.