On , I learnt ...

SSH config supports multiple host patterns in one block

From man ssh_config:

Host Restricts the following declarations (up to the next Host or Match keyword) to be only for those hosts that match one of the patterns given after the keyword. If more than one pattern is provided, they should be separated by whitespace.

and so you can do this:

Host 10.0.20.* 10.0.28.* 10.0.29.* 10.0.30.*
    User ubuntu
    IdentityFile ~/.ssh/xxx/id_rsa
    ProxyJump some-bastion-host
    StrictHostKeyChecking no
    UserKnownHostsFile /dev/null

where multiple host patterns are used for one block.