Yes you can, inside the input where you put the name of the domain you put mysub.domain.com and then you need to add a CNAME dns record.
IDK what you use to manage your domain, presumably linode dns manager but all you need is:
| type | hostname | value |
|---|---|---|
| cname | sub.domain.com | your.netlify.com |
Often all you need to specify in the hostname is the name part of the subdomain (in this example it’d be just sub, and often the TTL is fine as the default value (1 hour).