In a virtual machine, VirtualBox 6.1.26 installed FreeBSD 13.0.
FreeBSD freebsd 13.0-RELEASE-p4 FreeBSD 13.0-RELEASE-p4 #0: Tue Aug 24 07:33:27 UTC 2021 firstname.lastname@example.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64
echo 'keymap="ru.win"' >> /etc/rc.conf
Next, I suggest you view the video.
The video contains sublets.
The login console incorrectly perceives the transition to the Russian layout.
Russian characters are not displayed.
Some characters, for example "a" ("ф" - in the Russian layout) are perceived as "System commands".
Strange graphics buffer behavior.
*** Bug 258139 has been marked as a duplicate of this bug. ***
The console is set to VGA text mode here, which doesn't support other than ASCII (with vt(8)), but it appears there are additional bugs here. To help narrow down the issue could you try a test not in text mode (i.e., remove hw.vga.textmode or set it to 0)?
Add hw.vga.textmode=0 in /boot/loader.conf. Displaying Russian characters works.
Some characters are interpreted as "System Commands":
"a" ("ф" - in the Russian layout) and "g" ("п" - in the Russian layout) are perceived as "return";
"i" - ("ш" - in the Russian layout) are perceived as "backspace".
Strange graphics buffer behavior is present.