[pazos]

Actually everything looks pretty good, so I have no idea of the root of your problem.

The directory where exports files are placed is "clipboard" under KO data dir (the same dir where ko is installed in most e-ink devices, /sdcard/koreader in android)

If you want to figure out where those files end on your device you can add a little change

diff --git a/plugins/exporter.koplugin/main.lua b/plugins/exporter.koplugin/main.lua
index 94b08b58..62c739c7 100644
--- a/plugins/exporter.koplugin/main.lua
+++ b/plugins/exporter.koplugin/main.lua
@@ -172,6 +172,9 @@ function Exporter:exportClippings(clippings)
             for k, v in pairs(self.targets) do
                 if v:isEnabled() then
                     v.timestamp = timestamp
+                    if not v.is_remote then
+                        logger.info("exporting to", v:getFilePath(exportables))
+                    end
                     v:export(exportables)
                     v.timestamp = nil
                 end

and do the export again. It should print something like:

05/10/22-15:48:01 WARN  exporting to ./clipboard/2022-05-10 15:48:01-all-books.json
05/10/22-15:48:01 WARN  exporting to ./clipboard/2022-05-10 15:48:01-all-books.txt
05/10/22-15:48:01 WARN  exporting to ./clipboard/2022-05-10 15:48:01-all-books.html

in your log.