There’s a bunch of themes ready to update, for example:
[License free update available] You have version 2.1.1 installed. Update to 2.1.5. Requires SP Version 6.2.0.
But, when I try to update them I get a forbidden access error message
And, for example, if I go to https://simple-press.com/uploads/downloads/simple-press/themes/default-2.0.0/default.zip&wpupdate=1
I get: