Having worked with ISE and switching for many years, I stumbled upon some weird configuration.
Using some newer IOS XE in a 9K switch, I found the following command:
aaa group server tacacs+ mygroup
server name test1
tacacs server test1
address fqdn yadayada.something.x
key 7 supersecretkey
Initial thoughts, wow - now I can use fqdn! (assuming some things of course). I ran into some issues testing it out, but I got it working using kind of the above configuration. The fqdn points to a a-record and all where good. Main idea is to be able to change server ip without having to reconfigure all network devices if that is needed at some point (already done it once and I rather not do it again).
Problem is - I find little to no documentation on this command, when it was introduced, and for what versions. As we do not have the same image on all out switches, it´s hard to set a policy for it.