What are the risks or limitations associated with using Let's Encrypt certificates?

Main risks and limitations when using Let's Encrypt certificates:

• Short certificate validity period — usually 90 days, which requires automatic renewal; otherwise, the certificate will expire and the site will become inaccessible via HTTPS.
• Request limits — there are limits on the number of certificates issued and renewed per day, which can be problematic for mass usage.
• Support only for domain certificates — does not issue certificates for organizations (OV) or extended validation (EV).
• Dependence on automation — to ensure timely renewal, automatic scripts need to be configured; otherwise, downtime may occur.
• Some incompatibility with outdated devices — although support is broad, some very old systems may not recognize the Let's Encrypt root certificate.

Overall, Let's Encrypt is excellent for most projects, but these points should be considered when planning infrastructure.