https://javadl.oracle.com/webapps/download/AutoDL?BundleId=243727_61ae65e088624f5aaa0b1d2d801acb16
1, Download “jre-8u271-linux-x64.tar.gz” from [SEE ABOVE]
(Or if the above link is no worky, then https://www.oracle.com/java/technologies/javase/javase8u211-later-archive-downloads.html (you want the JRE! not the JDK, so scroll down a bit on the page for the “Java SE Runtime Environment 8u271” section))
as root (sudo su):
2, mkdir /usr/local/java (if not already exists)
3, cp “jre-8u271-linux-x64.tar.gz” /usr/local/java
4, cd /usr/local/java
5, tar zxvf jre-8u271-linux-x64.tar.gz
6, rm jre-8u271-linux-x64.tar.gz
7, update-alternatives –install “/usr/bin/java” “java” “/usr/local/java/jre1.8.0_271/bin/java” 1
8, update-alternatives –config java (select the number of the newly extracted one, it was #3 for me):
* 3 /usr/local/java/jre1.8.0_271/bin/java 1 manual mode
9, echo “JAVA_HOME=/usr/local/java/jre1.8.0_271” | tee -a /etc/default/unifi
10, reboot and enjoy.