SecureGeoPackage in QGIS

Quick start. Five steps; the same five in ArcGIS Pro and in the standalone program.

1Set up, once
Plugins > SecureGeoPackage. On the Access tab press Set up...: a pseudonym, then Create a new identity. Press Save public ID... and send that file to the admin of the file you need.
IDENTITY
no identity on this computer yet
Set up...
You are set up. Save your public ID and send that file to whoever owns the file you need.
2Open
On the Content tab press Open... and choose the encrypted GeoPackage. The line under the file name says your role and what you can do.
FILE
Open...
harbour.secure.gpkg
✔ signatures OK   your role  WRITER 
3Look
The tree shows the layers as your key opens them: a lock for an encrypted layer, green when it opens for you, grey BLOB when it does not.
LAYERS
🔒 soundings   ✔ opens with your key
   depth   REAL, encrypted
🔒 ukho_grid   egpkg_payload BLOB no key
4Decrypt, edit, save
Select the layers you want in the tree, or none for all, and press Decrypt: they appear in the QGIS project. Edit and save exactly as you always do.
FILE
Decrypt
Your layers are in the map. Edit and save, then press Encrypt.
5Encrypt
Press Encrypt: your edits go back into the file under its keys, the layers leave the project, the working copy is removed. Closing QGIS does this for you if you forget.
FILE
Encrypt
encrypted into harbour.secure.gpkg; working copy removed
If you see......do this
You are not on the roster of this filePress Request access...; it saves your public ID file and opens a mail to the admin: attach the file, send. When the admin has granted you, open the file again.
A warning that says PRIVATE IDStop and read it. Only the .publicid file ever leaves your computer.
That code is not validThe authenticator app and the computer clock must agree; wait for the next code and try again.
SIGNATURE INVALIDDo not use the file. Ask the sender for a fresh copy.
A layer shows one BLOB columnYour key does not open that layer; only the admin can grant it.
Nothing happens when you press EncryptThere is nothing to encrypt yet: press Decrypt first, or tick a layer.
You are the admin and someone sent you a .publicid fileAccess tab, Grant..., Pick public ID file..., choose a role.

The full manual is behind the ? button. A private production by Captain Ahab & Cosmo.