Inferior to machines at almost everything? Most jobs are safe, look at the 25 most common jobs in the US - cashier, food preparation worker, stocking associate, laborer, janitor, construction worker, bookkeeper, server, medical assistant, bartender, administrative assistant, marketing specialist, police officer, electrician, mechanic, etc.
In theory, if all developers are replaced, they should be able to find a different job. The problem is that the different job may have lower pay and status.
There's really no need for UBI.