Unable to register an alternate f-droid repo protected with let's encrypt on android 7.0 device

• Device OS and version: Android 7.0
• Device model/manufacturer: Samsung Galaxy Tab
• F-Droid version (in the About screen): 1.20
• F-Droid privileged extension version (if installed): -

What did you do? (clear steps if possible)

Tried to add the IzzySoft (https://apt.izzysoft.de/fdroid/) repository

What did you expect to see?

Being able to reach the new repository content

What did you see instead?

javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.

Please, provide a way to not rely anymore on the outdated system certificates for the repository access via network. For example, use something like OkHttp (https://github.com/square/okhttp) and offer a way to get updated root certificates (eg from https://curl.se/docs/caextract.html) to keep old platforms running.