Old Android device having problem with "SSL letsencrypt"

[dungvu]

Summary

Cannot access RTA sites using “SSL letsencrypt”, common symptom is unable to SIGN IN using SSO (KeyCloak) method
Video

Screenshot

Solution

Manually installed cert:

• isrgrootx1.cer (1.9 KB)
• lets-encrypt-r3.cer (1.8 KB)

Reference/Guide to install

• https://knowledgebase.geolantis.com/HOW%20TO/how-to-install-root-certificate-on-android-6-0-device/
• Or: