Hello,
If you would like to use SSH, you should rather buy Turris MOX or Turris Omnia. Because Turris Shield is meant to be for non-experienced users as there you can find only simplified reForis. More details can be found in the post of my colleague here:
Right now, we have two UIs (three if I don’t count LuCI which comes from OpenWrt). Foris was with us since the beginning and no new features are planned there maybe some small bug fixes, but these days we are focusing on reForis, which is now installed side by side with Foris on Turris 1.x, Turris Omnia and Turris MOX routers as some features are still missing in reForis.
If you do any change with SSH/LuCI on Turris Shield, we will provide only limited support if any.
Regarding this issue:
This is going to be fixed in Turris OS 5.1.1, which is currently in Testing branch.