Quick reminder: The Nazi German government emptied out Eastern European towns and villages taken by the Wehrmacht during various campaigns, most notably Operation Barbarossa, for resettlement of "pure" Germans to those occupied lands (called Lebensraum)... this started almost literally once these occupied towns and villages were far enough from the front lines. Also, the whole point of the US Government's genocidal forced march of native tribes, often referred to as the Tail of Tears, was to clear said native tribes out so the Southern aristocracy could seize the land for plantations worked by chattel slaves... whole swaths of what is today Florida, Georgia, Alabama, and Mississippi were settled by whites as a result.
Many a "populist" (read: Fascist or proto-Fascist) operate their politics in this manner. Promise either cheap land (or, at the very least, housing) to the workers and others by committing what is, on it's face, a genocide. There's more modern examples (two in particular, going on right this minute for all the world to see), but I don't want to get the ban-hammer so I won't name them directly (I forgot to check the instance in which I am commenting before doing so, but not taking my chances).
Pretty much any time in human history where someone has tried to displace that many people, they've either failed or it turned into an ethnic cleansing.
This wouldn’t be rounding people up based on their ethnicity.
It would not be rounding people up
It would not be based on ethnicity
Instead:
It would be applying a particular dispatch when people encounter the legal system
It would be based on legal status
So in the same way that a government could have a policy like
IF you are stopped while driving drunk THEN you will be put in a jail cell for drunk people
this would be a policy like
IF you are brought into custody and we determine you’re here illegally THEN we will deport you
So no, this isn’t in any way like rounding people up (ie performing a dragnet across all of society to ferret people out) based on ethnicity. Like, at all.
Let's say you suddenly got yanked from your home and sent to live in the land of your ancestors (where you don't have a home or any friends). Would you survive?
If yes, ask yourself again, but now you're broke and have a medical condition and you require medication to survive. How about now?
These people getting deported don't have 2nd homes they can return to, and they can't just put one on a credit card.
Don't like homelessness? Mass deportation creates homelessness crises.