Looking for a All in One Laser Printer

The issue you run into with All-in-One scanner/copiers is assigning the usb port to be a scanner vs a printer. I believe that only print/hplip handles switching out of the box. print/hplip is written upstream by Hewlett Packard and IMHO, is somewhat bloated and buggy. Some of the newer All-in-Ones made by Brother/Canon have a NIC interface + usb - perhaps the printer can get the NIC and the scanner the usb?

I use a Brother printer on NIC as a network printer and a Canon usb scanner that I'm happy with.
What printer do you have? I can get a separate scanner if that makes a big difference.
It does! If you want all-in-one laser you are pretty limited to $300+ HP devices (via already mentioned HPLIP drivers) or more if you want color printer. Most better devices can scan to local mass storage or even e-mail scans so sane-backends are not really needed nowadays. You could get a Brother 5250 which is an excellent monochromatic laser printer (full PostScript) and one of older Epson scanner or even all-in-one work well. I have Epson Perfection 1670 and WorkForce 845 all-in-one next to me. The problem with WorkForce is that printer is paper weight but scanning, color coping (it is ink-jet) works as a charm. Bonus with WorkForce is ability to print from my smart phone.

I really like Brother monochromatic printers and all-in-one but you will not find open source drivers for their scanners (Linux drivers have hidden binary blobs).
Most of your applications output print jobs as either text or postscript. Postscript was developed by Adobe and use to require a license. Adobe open the specification which allowed printer manufacturers to produce their own postscript emulation. HP, Brother, Okidata, Lexmark and Canon all have their own postscript emulation in their higher end printers. Postscript printers generally have a wider selection of embedded fonts and process the print job quickly

A cheaper laser based on PCL5/PCL5e/PCL6 is also easy to setup in FreeBSD and would be an option if your printing needs are light. The postscript output has to be processed by the PCL driver prior to being sent to the printer so they are slower. The Brother HLL-2360 supports PCL6 and I can vouch that pxlmono driver in print/ghostscript9-base worked well for the older HL-2270.
I bought a second hand Kyocera KM-2810. It is a little bit dated, however I paid only US$ 120 for it, and this was my best printer purchase in the last 3 decades.

It came with a built-in SMB client for sending the scans to a SMB network share. Using net/samba44, I setup a network share called Scanner on my FreeBSD server, and the Kyocera scanner copies without any hickup its 600dpi color scans as .pdf-files into that samba share. With that technology you won't need a dedicated scanner driver, and once gotten used to the very simple scanning workflow, you can be sure that you even don't want anymore any scanner driver.

The printer itself comes with PS3 emulation and should work without any special driver.

I did not check it, however, I am almost sure that the recent Kyocera All in One models offer similar features. Perhaps even other brands offer some kind of a Scan to a Network Share and/or USB volume facility. You want to look out for it.
I got a XEROX WorkCentre 3220 some years back because it accepts postscript and so works well with FreeBSD. It's been great and the ink costs about $95 for 4,000 pages. I see they're cheap on Amazon now.
I guess that Kyocera ecosys M5521cdw should work fine as it supports PCL 6 (PCL 5c/PCL-XL), PostScript 3 (KPDL 3), PDF Direct Print 1.7, XPS Direct Print.
As for scanner it supports scan-to-email, scan-to-SMB etc, so no scanner drivers needed.