On Chain of Trust - Let's Encrypt, it is said:
Almost all server operators will choose to serve a chain including the intermediate certificate with Subject “R3” and Issuer “DST Root CA X3.”
As far as I understand, the now recommended version of "R3" to send is the one issued by "ISRG Root X1". If that is right, the above sentence needs to be updated.
Not taking minor changes around that specific piece of info into account, that sentence is 5 years old: it was part of the initial upload of the website back in 2016.
It should have been updated back in May this year already.
I checked the github repo earlier, and there was no Issue or PR to update this page. Someone could/should if they have time. I am swamped on other projects today.
Done.
Dang, it's already merged! Nice 