If they do have an ID.me / IRS account it's super easy to get the IP PIN.  I was part of the National Whatever Whomever data breach last year so I went ahead and got the PIN last month when they reopened.  Took me longer to log into my IRS account than to click a couple times and get a PIN.  I haven't filed yet so I'll find out in a couple weeks if it works.  I'm tempted to try filing without it just to see if it (properly) gets rejected.