Thanks for the screen photos.
If I understand this correctly, You installed TrueOS on a non-ZFS filesystem (UFS/UFS2/FFS). Am I right? Please, confirm.
If I understand Your original post correctly, presently You can boot into none of Your 3 operating systems. Is this correct?
If You can’t boot into any of Your operating systems,
You should try to rewrite the Master Boot Record of ada0.
I would try this with all of Your operating systems while booting Your hardware from their rescue-ers/install-ers, one after the other. The order of doing this I recommend would be: TrueOS, Linux, Windows.
Let’s start with TrueOS:
TrueOS booting consists of three stages on MBR-disks.
Those are (re-)installable/initializable with:
“gpart bootcode …”.
Please, read “man gpart” and look for “boot” in there.
Afterwards, boot from installer, make sure Your root-filesytem from ada0 gets mounted somewhere, then do a change-root to this mountpoint. Afterwards enter “mount -a”. Now You can reinstall Your bootstrapping code again, using the software from Your ada0-TrueOS.
Your root filesystem is presumably “ada0s4a”.
Afterwards, reboot and check.
The same technique can be used with Linux to re-install GrUB, if necessary.