Forgive me but I'm pretty green when it comes to these F5's. We have an F5 LTM that is load balancing our internal and external email. We just had a pen test done and they saw TLS1 and 1.1 open from ...
Ok lets start from a test. If you can find a device that runs nmap that can get to the external interface try running this, nmap --script ssl-enum-ciphers -p 443 <Your domain name here.com>
This should show you what you are dealing with and a method to prove that its worked!
Then under your ssl profile you need to chnage the config from "Basic" to "Advanced" Then you'll see the Options List
Here is mine, it appears its flow down so NO DTLSv1.2 turns off everything below that and leaves TLSv1.3. I don't know a location to see where a profile is used in a virtual server, but if you get a ucs file or the internal conf files out using the cli you could do a quick word search in the config maybe?
But you can go into the certificates and see which profiles they are used in which might get you "close" to the same place.
Now, i used the cyphers profile which also controled tls1.0, 1.1 1.2 etc. And no tls1.3 basically turned it all of. But i needed that nop dtls1.2 for it to work. So maybe one is covering up the other thinking about it.
The best thing to do, is run that nmap command so you can see what you are playing with and work from there.
yeah i think i made a mistake as the cypher profile overrides some of that config and made it work. no tls1.3 will not enable it, the config is a bit backwards. "enable" NO TLS for example is a positive then a negative. So if you want tls 1.3 then you need to take that out of enable options.
This issue i thnk i had, is that enable options needs something in there to work.
Have you got a test environment you could look at and test before you do this to see what happens.