🇷🇸Serbia csbt23
"I think it needs to be mentioned that you cannot update from 9 > 10 manually. It's not possible."
That's not true. I personally updated a bunch of sites from 9.5.11 to 10.x "manually". In most of the cases you need to clear the cache after you swapped the core and vendor folders but before you reload the site, otherwise you'll get various fatal errors. Of course clearing the cache can also be a challenge if you can't use Composer and/or Drush as the admin UI is also unusable at that point.. Perhaps you have DB access so you can truncate all the cache_* tables.
So it's tricky and definitely not the suggested way to upgrade a site to D10 but far from being impossible.
🇷🇸Serbia csbt23