Well let's break it down then, per your link. The number they deem "mostly true" comes from a couple of sources, one of which is MIgration Policy Institute.

One of MPI's principal findings is that the deportation system has dramatically changed over the past 19 years – moving from a judicial system prior to 1996, where the vast majority of people facing deportation had immigration court hearings, to a system today of nonjudicial removals, where 75 percent of people removed do not see a judge before being expelled from the U.S.

So let's look at that ". . . moving from a judicial system prior to 1996" - what happened in 1996?

Well according to this,

The 1996 Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) was a momentous law that recast undocumented immigration as a crime and fused immigration enforcement with crime control (García Hernández 2016; Lind 2016). Among its most controversial provisions, the law expanded the crimes, broadly defined, for which immigrants could be deported and legal permanent residency status revoked. The law instituted fast-track deportations and mandatory detention for immigrants with convictions. It restricted access to relief from deportation.

Now I'm pretty sure you can grok it from here but for the sake of wrapping it up:

The document noted that nonjudicial removals included "expedited removals," "reinstatements of removal" and "stipulated removals," clarifying that stipulated removal orders "are signed by an immigration judge, but typically do not involve a removal hearing." . . . This figure originated from the DHS's 2013 Annual Report "Immigration Enforcement Actions" (Page 1), which shows that 44% of removals that year were expedited removals, while 39% were reinstatements of prior removal orders — together accounting for roughly 83% of total removals during that fiscal year (Oct. 1, 2012 to Sept. 30, 2013).

And finally

As outlined in DHS documents, "expedited removal" refers to the removal of a noncitizen "who is inadmissible because the individual does not possess valid entry documents or is inadmissible for fraud or misrepresentation of material fact." Under this process, individuals may be removed without a hearing before an immigration court.

So

I truly do not understand how your characterization of these deportations follows

It follows thusly: People who appear at the border without paperwork (visa, immigration status, asylum status, other) are not subject to trial, they can be turned away. Additionally, people without paperwork who have already been told to leave but have not can be removed without trial. This is not based on Obama's policy. This is based on a law from 1996, which as you well know is before Obama or Biden became President.

These bureaucratic legal walls to immigration are not particularly fair much less ideal, but they are a reality of a national border. In particular, that border policy from 1996 changed the way it had been handled for decades up to that point and created the system Obama inherited which he abided by. He did not carry out raids the likes of which we've seen in the past six months and he did not sanction them, which is what the comments about the meme are suggesting.

My point, then, is that there can be "3.1 million 'deported'" based on a very loose definition of a practical daily event at the border, or related border findings, and it does not mean the insanity and chaos of ICE and associated Constitutional quagmires as created by this idiotic administration, where they're removing people who have visas, who have residency status, who did not commit fraud, etc. etc.

But people don't want to look at nuance in any way shape or form, and the so-called-left would rather take that loosely-worded mostly-true fact and demonize the Democrats so that they can pat themselves on the head for being ultra-left-überprogressives who don't need to vote. I disagree with it.