No AppStore after Update / installed Apps does not run

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Nextcloud version:
Operating system and version: openSUSE Leap 15.2
Apache version: 2.4.33
PHP version: 7.2.5

The issue you are facing:
The AppStore is not visible after the update from NC18 → NC19 → 20.0.8. Only the installed Apps are visible. So I can not update my Apps. The recommended step after the update (occ db) are done.

I have downloaded the apps shown as disabled by hand and installed them via occ. (calendar, contacts, files_markdown, cms_pico, twofactor_totp) some of them seems to run (twofactor_totp). But the other apps seems to struggle

Is this the first time you’ve seen this error?:
No, I see this error on older verions (NC 17) There were some hints to edit the TimeOut. After this the Appstore was shown.

The output of your Nextcloud log in Admin > Logging:
There are a lot of such lines

/appinfo/app.php is not loaded when \OCP\AppFramework\Bootstrap\IBootstrap on the application class is used. Migrate everything from app.php to the Application class.

Meanwhile I have removed the apps cms_pico and files_markdown. So these messages are gone. But the ical does not run as bevor. I get these message when try to open the ical-url in a browser:

Internal Server Error
The server was unable to complete your request.
If this happens again, please send the technical details below to the server administrator.
More details can be found in the server log.
Technical details
Remote Address:
Request ID: TrCsvrYEMPEmy7cO5EWm

Any hints?

I try to get and install the app files_markdown with
# sudo -u wwwrun php occ app:install --keep-disabled files_markdown
Error: Could not download app files_markdown

but there are no entrys in the nextcloud.log.

Can you ping the server and download an app directly via wget?

Yes, ping and DL the apps was possible … but there where more probs after this …

I have removed this instance and start a new test with the latest version.

Thx for your answer!