To be honest, tried installing KDE Neon twice to see if it was only a glitch.
Both occasions, different .iso was used.
Problem occurred in both instances.
While not wanting to privilege MX Linux in any way over KDE Neon…
Have installed its KDE iteration twice, and in both instances, login into Gmail was a no brainer.
An issue of ad blocker having issues with Youtube blocking Firefox 119 on Windows does not happen on MX KDE (presently using), nor with Vivaldi (used on both systems).