Understood Oliver but you have to use what is operationally necessary to do your job properly.
If your org is that security aware then you should only be accessing the WLCs from a secure jump server with no internet access and only by authorised admins which largely mitigates any risks due to using an outdated browser and you raise an appropriate entry for it on your risk register with whatever exemption or waiver you have to get.
As others have pointed out http access will likely also work but that is also insecure because username/passwords will get sent in the clear so a mature, adult, informed discussion with your security team about which is the lesser evil may be necessary. Given that choice they may prefer an older browser version. If you insist on only using the latest browser you're going keep encountering these problems repeatedly. Remember AireOS is approaching end of life now so Cisco will not be putting much, if any, time into fixing this type of problem.
Of course your other option is to do everything on CLI over SSH. Apart from making sure client and server support the same ciphers and hashes you have no more of those display issues and it's secure.
