Update:

It seems that the maximum number of notes for Evernote Personal (the cheapest paid plan) has now been pushed from 100,000 to 150,000:
https://evernote.com/compare-plans

This should keep me going for a couple of years more...

Plus, some news:
https://www.theverge.com/2024/9/15/24242764/evernote-future-productivity-app-vergecast


Alexander Deliyannis wrote:

It is possible that you've already reached the system limit of 100,000
notes. Please know that there is an Evernote system limit that the
maximum number of notes in an individual account is 100,000. Please try
deleting more notes and make sure to also delete them from the trash.