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What problem did you encounter?
When clicking news in the menu, you see the templates loading and then it stays blank. This happens in recent versions of Chrome(-based) browsers (versions 87, 88).
In the inspector you see there is an issue with Content Security Policy related to eval
Explain what you did to encounter the issue
I don't think it's relevant since the mobile app and firefox are working
Read http://ggnome.com/wiki/Using_The_Browser_Error_Console if you are unsure what to put here
globals.js:60 jQuery is deprecated: The global jQuery is deprecated. It will be updated to v3.x in Nextcloud 21. In later versions of Nextcloud it might be removed completely. Please ship your own.
ie @ globals.js:60
get @ globals.js:91
(anonymous) @ sideMenu.js?v=dde4e8d0-4:7
setTimeout (async)
retrieveApps @ sideMenu.js?v=dde4e8d0-4:7
childList (async)
re @ jquery.js:4377
we @ jquery.js:5238
prepend @ jquery.js:5440
(anonymous) @ apporder.js?v=dde4e8d0-4:24
each @ jquery.js:365
mapMenu @ apporder.js?v=dde4e8d0-4:23
(anonymous) @ apporder.js?v=dde4e8d0-4:50
l @ jquery.js:3187
fireWith @ jquery.js:3317
M @ jquery.js:8757
(anonymous) @ jquery.js:9123
load (async)
send @ jquery.js:9142
ajax @ jquery.js:8656
m.each.m.<computed> @ jquery.js:8807
(anonymous) @ apporder.js?v=dde4e8d0-4:29
l @ jquery.js:3187
add @ jquery.js:3246
m.fn.ready @ jquery.js:3496
m.fn.init @ jquery.js:2927
e.fn.init @ jquery-migrate.min.js:2
m @ jquery.js:75
(anonymous) @ apporder.js?v=dde4e8d0-4:1

I am experiencing the same issue, but in my case it does not appear that CSP is the issue... The template shows up, but then disappears and I have to reload the page at least 2 time for it to load correctly. Seems like an issue with Chrome (And related) specifically... Works fine on Firefox.
(Wish I could use Firefox at work, lol)
Edit: Interestingly, if I open dev tools, it never loads at all until I close dev tools...
The Webinterface is very outdated and as fast as the web develops probably more than a few things are outdated and unsupported. Also it might conflict with the current Nextcloud versions.
We didn't have a front-end developer for years for Nextcloud, only small changes to a few lines of code were made, but to say it short it's beyond repair.
Recently work to replace the fronted with a version that is better and based on vue.js started, vue.js became the standard within the Nextcloud org.
If you can and and you are interested check out the list of pull requests and participate there, create mockups or provide feedback later.
Don't be disappointed if this gets closed automatically later, we don't have the will to manage 100 or a 1000 open issues that don't make any progress at all.
Ok, we'll see when it will work again
Most helpful comment
The Webinterface is very outdated and as fast as the web develops probably more than a few things are outdated and unsupported. Also it might conflict with the current Nextcloud versions.
We didn't have a front-end developer for years for Nextcloud, only small changes to a few lines of code were made, but to say it short it's beyond repair.
Recently work to replace the fronted with a version that is better and based on vue.js started, vue.js became the standard within the Nextcloud org.
If you can and and you are interested check out the list of pull requests and participate there, create mockups or provide feedback later.
Don't be disappointed if this gets closed automatically later, we don't have the will to manage 100 or a 1000 open issues that don't make any progress at all.