I can confirm this currently being exhibited on a TOS4.x node. For some reason the package luci-compat would seem to be absent at the upstream [1] repo and thus not being available throuhg the TOS repo either.
Probably best to lodge a package request with upstream development.
[1] https://downloads.openwrt.org/releases/18.06.5/packages/arm_cortex-a9_vfpv3/