The ACME protocol is open and as a result there are several alternative clients which do not require root. Here's a few:

https://github.com/diafygi/letsencrypt-nosudo

https://github.com/kuba/simp_le

https://github.com/lukas2511/letsencrypt.sh

Or you can go a more manual approach via https://gethttpsforfree.com/ but you will need to manually renew your certificate every 90 days.