I have upgraded jenkins to 2.319.1 and started seeing this issue.
Our Jenkins is accessed via Netscaler endpoint. https://company.internal.com/jenkins.
Earlier I used to access via host:8080 format. i.e http://host:8080/jenkins and everything was working. It still works fine when accessed like that.
Image 1 : When accessed via Netscaler
Image 2 : When accessed via ip
What I tried so far.
Are there any plugins which can provide icons.I have tried dark theme and simple theme plugins, but to no avail.
Update : I narrowed down the last working version
LTS : https://archives.jenkins-ci.org/redhat-stable/jenkins-2.303.3-1.1.noarch.rpm
Regular : https://archives.jenkins-ci.org/redhat/jenkins-2.307-1.1.noarch.rpm
Update 2
svgs are present in /var/cache/jenkins/images folder. They wont load in browser.
Finally we found the solution. We had a http to https redirection policy in Netscaler. We dont know why that was blocking *.svg images. The policy is turned off and now jenkins is working great.All the images are loading properly and functionality is working fine.