Found a missing word.
I look forward to have this feature, thanks for implementing it.

typo fixed

For maximum compatibility, I'd strongly suggest that hw.vt.textmode=1 for BIOS implementations (at least for 13) since that's historic behavior and there's no where near enough time to gather additional data. Since we're deployed overwhelmingly to server systems, and server systems tend to be harder to recover from failure than laptop/desktop, I'd hope this goes in like that. Many console redirectors work in text mode, but fail in graphics mode, for example.

The rest of this patch is too long for me to meaningfully review, alas

In D27420#613954, @imp wrote:

For maximum compatibility, I'd strongly suggest that hw.vt.textmode=1 for BIOS implementations (at least for 13) since that's historic behavior and there's no where near enough time to gather additional data. Since we're deployed overwhelmingly to server systems, and server systems tend to be harder to recover from failure than laptop/desktop, I'd hope this goes in like that. Many console redirectors work in text mode, but fail in graphics mode, for example.

The rest of this patch is too long for me to meaningfully review, alas

ACK, the default build updated and compile time knob added.

Notable side effect of setting kern.vt.fb.default_mode: switching from efifb to GPU fb does not increase resolution.
Fun effect with Radeon GPUs: a GOP mode with the wrong aspect ratio will be stretched, but GPU native framebuffer setting the same resolution via kern.vt.fb.default_mode will instead be pillarboxed :)

Big thanks for doing that though: this (in combination with a mainboard upgrade) has caused me to play with efi_max_resolution and gop mode setting and that led me to an interesting discovery about The Radeon EFIFB Conflict Bug™ (namely that it happens for me specifically with GOP mode 0, which is the "closest to native" — 2560x1440 on a 4k screen)

After booting with the font applied by the loader, applying a font with vidcontrol panics with a general protection fault:

[2] --- trap 0x9, rip = 0xffffffff8048f91d, rsp = 0xfffffe0115a76fe0, rbp = 0xfffffe0115a77010 ---
[2] free() at free+0x4d/frame 0xfffffe0115a77010
[2] vt_change_font() at vt_change_font+0x171/frame 0xfffffe0115a77060
[2] vtterm_ioctl() at vtterm_ioctl+0xf30/frame 0xfffffe0115a770b0
[2] termtty_ioctl() at termtty_ioctl+0xc5/frame 0xfffffe0115a77100
[2] tty_ioctl() at tty_ioctl+0x3b/frame 0xfffffe0115a77140
[2] ttydev_ioctl() at ttydev_ioctl+0x26d/frame 0xfffffe0115a77190
[2] devfs_ioctl() at devfs_ioctl+0xc7/frame 0xfffffe0115a771e0

Can the performance be improved? There's a noticeable delay before the screen with the images pops in. (Could that actually be time spent on mounting ZFS?) Somehow rEFInd draws its graphics much much quicker.

From a quick look at the code, the drawing API is tied to the character grid? :/
Would be cool to eventually add a different menu that shows like a minimal single line below the OEM logo (BGRT), and that logo has pixel coordinates.

This made the only amd64 FreeBSD system that I have access to display a blank
screen in the loader. It is a ThreadRipper 1950X system.

The camera recorded a \ with an underscore under it before the screen turned
completely blank. For the time with \, it did not seem to be changing.

Then there was a blank screen until . . .

The first image after the bank screen as captured by the
camera was the "Welcome to FreeBSD" display with selections 1.
to 5. and options 6. and 7. shown, where it also said:

  Autoboot in 0 seconds, hit [Enter] to boot or any other key [edge of picture]

Loading kernel...
/boot/kernel/kernel text= *** I OMIT DETAILS ON THIS LINE ***
*** I OMIT DETAILS ON THIS LINE ***
Loading configured modules...
/boot/entropy size=0x1000
/etc/hostid size=0x25
/

That last may just be timing of the imaging. (I used fast repeat
instead of video.)

The system is not configured to EFI boot FreeBSD. The FreeBSD boot media
has just:

# gpart show -p /dev/nvd2
=>        40  1875384928    nvd2  GPT  (894G)
          40        1024  nvd2p1  freebsd-boot  (512K)
        1064  1468006400  nvd2p2  freebsd-ufs  (700G)
  1468007464   402653184  nvd2p3  freebsd-swap  (192G)
  1870660648     4724320          - free -  (2.3G)

Adding:

hw.vga.textmode="1"

to /boot/loader.conf made no difference.