Cannot open doc, docx, xlsx, odt, ods, txt files

Expected behaviour

Able to view and edit common office documents, such as doc, docx, odt, xlsx, ods, txt files, with Nextcloud's built-in viewer.

Actual behaviour

Cannot view or edit common office documents, such as doc, docx, odt, ods, txt files.
It shows a white page, then with an error:
cURL error 3: malformed (see https://curl.haxx.se/libcurl/c/libcurl-errors.html)

Txt was supported a while ago, but lately it couldn't be opened any more.

Steps to reproduce

Server: snap 19.0.2snap1
Client, iOS 3.06
Open up a doc, docx, odt, ods, txt file,

Reasoning or why should it be changed/implemented?

These files are very common in an office environment, so it's probably expected that these files can be opened by the built-in viewer.
Your competitor Dropbox can open them.

iOS version

13.6.x

App version

3.6.x

Server configuration

Snap 19.0.2snap1

Operating system:
Server: ubuntu 20.04
iOS App: iOS 13.6

Web server:
snap built-in

Database:
snap built-in

PHP version:
snap built-in

Nextcloud version: (see Nextcloud admin page)
19.0.2

Thank you.

Start by reproducing the failure in the Nextcloud iOS app with the reported Nextcloud 19.0.2 snap server and the listed document formats. Trace the built-in viewer request that produces the “cURL error 3: URL malformed” message, including the previously supported TXT case. Done means the reported office documents open without the white-page error.