Zenfone 8 hanging at startup - please can anybody remind of ground zero re-installation?

[fergusd84]

My wonderful Zenfone 8, more than 2 years in, just hung at re-start showing "Zenfone" and slithering 4-colour dots.
Long presses, short presses, .. .., nothing moves it along.
Before I send it to UK Support for ground zero re-installation of OS (assuming they can do it??) can I try to manage this myself?
I have a strong memory of a website to visit with some kind of zipped target but (a) have forgotten its address; and (b) is it only for firmware update on a working phone rather than firmware  re-installation of a hung phone (which is what I've got!).
Many thanks for any illumination and preferably instruction!
PS I can't even get at its serial number.

[fergusd84]

PS Should have said: it's stuck at this (slithering dots). I haven't found a way even to turn the phone off, far less to advance.
Long press <VolUp>+<Power> which should lead to Fastboot Mode and a re-installation opportunity has no effect.
So probably things are not looking good for self-repair either .. .. :o(

[fergusd84 · Accepted solution]

Sorry, me again. Just in case it helps anybody else.
The phone was endlessly slithering. Longpress <VolDown>+<Power> did the trick. After a few seconds the screen blanked and immediately I moved to <VolUp>+<Power> and from there was able to select Factory Reset.
A significant pain to have lost all Settings, Preferences, Histories, Installations, Threads, blah blah blah .. .. but 1000 times better than sending the phone back to ASUS UK or losing it altogether as a mere doorstop.
No idea at all what caused the hang .. .. ..