My son has a Likeabike Jumper which is fantastic, but he started off on a Puky LRM which was also great and small for the tiny ones.
We did add a front brake to the Jumper (Likeabike sell one) and while it works fine it doesn’t really help on steep hills as the bike just tips forward – he can come down the same hills fine on his pedal bike using just a front brake as he can get his weight back.
I do feel that just having a rear brake on a balance bike will encourage kids to just use their back brake when they start riding a pedal bike and they won’t realise how much more control you have using your front brake. (or am I over thinking this…)