Explanation
SELinux is not blocking this operation. SELinux is a security module that enforces mandatory access control policies on Linux systems. SELinux can restrict the actions of processes and users based on their security contexts and labels. However, SELinux does not prevent a user from setting the system time from inside a Docker container. The reason why a user's attempts to set the system time from inside a Docker container are unsuccessful is because Docker containers share the same kernel and clock as the host by default. Therefore, changing the system time inside a container requires privileged access to the host kernel, which is not allowed by default for security reasons. To allow a user to set the system time from inside a Docker container, you need to run the container with the --privileged flag or the --cap-add SYS_TIME flag. References:
https://docs.docker.com/engine/security/selinux/,
https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities

Explanation
This command will not mount the host's '/data' directory to the ubuntu container in read-only mode, because it has several syntax errors and missing options. According to the official documentation, the correct command should be:
docker run --volume /data:/mydata:ro --read-only ubuntu
The errors and missing options are:
The --add-volume flag does not exist and should be replaced by --volume or -v to mount a host directory as a data volume.
The --volume flag requires a colon (:) to separate the host directory and the container directory, not a space.
The --read-only flag applies to the whole container's file system, not just the mounted volume. To make the volume read-only, a :ro suffix should be added to the --volume flag.
The ubuntu image name should be the last argument of the command.
References: https://docs.docker.com/engine/reference/commandline/run/#mount-volume-v-read-only
https://docs.docker.com/storage/volumes/#use-a-read-only-volume

Explanation
Enabling mutual TLS between the Docker client and server is not the purpose of Docker Content Trust.
According to the official documentation, the purpose of Docker Content Trust is to verify the integrity and publisher of all data received from a registry over any channel.
References: https://docs.docker.com/engine/security/trust/content_trust/