I was just able to figure out a solution out for this. It seems that you now have to be running Java 11 for the Subversion plugin to work, though the base Jenkins installation still supports Java 8. I was running Java 1.8 and updated to using Amazon Correto Java 11. I noticed this when looking at the system log in Manage Jenkins > System log and saw that the subversion plugin was getting java version errors.
You will have to go in to Jenkins and edit the Java_home directory path to point to the location of your Java 11 home directory. I did this by going into the jenkins.xml located in the user.dir, which for me was located in C:\Program Files\Jenkins, and editing the java.exe path in the file to point to the Java 11 location. You can find the user.dir by going to Manage Jenkins > System Information and searching for user.dir. I also edited the windows environmental variables to include the Java 11 path, though I am not sure if that is necessary for Jenkins to find the path as that alone did not allow Jenkins to find the path.
After doing this, the java.home variable in Manage Jenkins > System Information now pointed to the Java 11 path and the subversion plugin was working correctly.
I would like to second this. I installed 2.16.0 and everything stopped. I have also tried everything I can think of and it is broken.