An update:
While looking at Wordpress > Tools > Site health
I noticed the Xdebug warning. Not thinking much and not able to pinpoint the php.ini location (seems there are many). I did a: sudo phpdismod xdebug
And then a wo stack restart
for --php73 -- php74 --nginx
On one site I get nice 100/100 PageSpeed. On others I probably have to do some re-tuning.
However, back to topic, /wp-admin/ runs fast again.
Seems Xdebug was the culprid.