I've had the same problem over the last week or so on a new RPi4, on 3 HDMI TVs out of 4 (but the 4th was the main 49" smartTV that was needed for other purposes).
It was a nuisance because all the most important bits (like the login/password prompts in text mode, or the main button on the GUI which is always right in the corner, or a full-screen editor display) are all off the edge of the screen!
For Raspbian, using 'sudo rpi-update' seemed to fix that, but with other test OSes, it is still an issue.
I wondered why the machine, in default mode, writes to the extreme edges anyway. Why not start off with generous margins and then configure it to use more of the screen area.
(Try editing config.txt in full-screen text mode with that crappy nano editor when you can't see the beginnings of the lines, not that that made any difference. The explanation about overscanning and whether the offsets should be positive or negative, was also very confusing. A 'bigger' or 'smaller' displayed image is a simpler concept.)
AIUI, and from my own tests with various displays, overscan needs and the "reporting" thereof, esp. by "newer" and "smartish" T.V.'s has changed
and this has unfortunately coincided with newer (improved) edid parsing/handling within Buster and the extra capabilities of the P4B. There are several others threads here which discuss progress (at the time of writing) and the most recent one I'm aware of is this: https://www.raspberrypi.org/forums/view ... 3&t=250675
which I link to from my own notes/example within my webpages here: https://www.cpmspectrepi.uk/raspberry_p ... erP4B.html
. W.r.t. "I wondered why the machine, in default mode, writes to the extreme edges anyway. Why not start off with generous margins and then
configure it to use more of the screen area." that's because, historically, as a "hangover" from C.R.T./composite video practice an overscanned display was expected. To confuse things further some newer T.V.'s may or may not expect an overscanned input depending upon which input is in use and whether or not the T.V.
"thinks" the source is a "P.C." (and may or may not report that behaviour within the edid info.).
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm