Hardware:
Dell T610 (in UEFI mode) 64GB RAM (in Advanced ECC mode) with H700 1GB cache w/BBU (Firmware Package Version: 12.10.7-0001) and 8 x 3TB (2.8TB) Dell (Hitachi) near line (7.2K) SAS 6 Gb/s drives.

RAID 10 Volume is empty and initialized. FreeBSD is the only OS.

When I configure all 8 drives in RAID 10 (11,176GB), I get an error during install:
No free space left on device.

Steps:
 1. Boot from 12.2-STABLE CD1 ISO (FreeBSD-12.2-STABLE-amd64-20210211-r369250-disc1.iso)
 2. at Welcome to FreeBSD!: Install (hit Enter)
 3. at Keymap Selection: Select (hit Enter)
 4. at Set Hostname: "local" (type in l-o-c-a-l)
 5. at Distribution Select: OK (hit Enter)
 6. at Partitioning: Auto (UFS) Guided Disk Setup (hit Enter)
 7. at Partition: Entire Disk (hit Enter)
 8. at Partition Scheme: GPT GUID Partition Table (hit Enter)
 9. Error: No free space left on device. <OK> (hit Enter)
10. at Partition Editor: Finish (hit Enter)
11. watch it install and set empty password
12. reboot
13. at loader: "Failed to load kernel 'kernel'

While I am at the loader, I'll check on devices:
Type '?' for a list of commands, 'help' for more detailed help.
OK lsdev
cd devices:
    cd0:    0 blocks (no media)
disk devices:
    disk0:    23437770752 X 512 blocks
      disk0p1: EFI
      disk0p2: FreeBSD UFS
http: (unknown)
net devices:
    net0:
    net1:
OK ls disk0p2:
open 'disk0p2:/' failed: no such file or directory
OK

Notice that there's no swap partition from using the "Auto" partitioning. I can't `ls` the boot disk partition #2, but FreeBSD clearly thinks there's something there it knows about, like a UFS partition.

On the same server, if I change the RAID 10 from using 8 drives to 6 drives FreeBSD installs and reboots without issues (I am using it this way now). With a 6 disk setup, the RAID 10 is 8,382GB in size. I can also "ls" the disk from the loader prompt:
Type '?' for a list of commands, 'help' for more detailed help.
OK lsdev
cd devices:
    cd0:    0 blocks (no media)
disk devices:
    disk0:    17578328064 X 512 blocks
      disk0p1: EFI
      disk0p2: FreeBSD UFS
      disk0p3: FreeBSD swap
http: (unknown)
net devices:
    net0:
    net1:
OK ls disk0p2:
disk0p2:/
 d  .snap
 d  dev
 {...}
    COPYRIGHT
 d  media
    entropy
OK ls disk0p2:/boot/kernel/
disk0p2:/boot/kernel/
    wlan_amrr.ko
    ng_pred1.ko
    {...}
    snd_envy24.ko
    snd_ds1.ko
OK

I was able to find someone else reporting the same issue, albeit on the (12th) generation of Dell PowerEdge's after the T610 (11th gen):
https://forums.freebsd.org/threads/cant-load-kernel-after-fresh-install.40810/

The OP changed the partition size from max (25TB) to 250GB to get FreeBSD to install and reboot successfully.

I'll upload serial console captures of the broken configuration with 11.1TB and from a working configuration with 8.3TB. Both captures are from the same box, the only difference being the working configuration has 6 x 2.8TB drives in RAID 10 (8.3TB total) and the broken configuration is all 8 x 2.8TB drives in RAID 10 (11.1TB total).