F-Droid 1.9 fails to install applications

You have phone Do Not Disturb mode on? Maybe that prevents F-Droid functioning properly. I would turn off do not disturb and try again.

You could try:

Settings, Apps, F-Droid, Force Stop; Storage, Clear Cache. Start F-Droid, swipe down for refresh. Install app.

If that doesn’t work, repeat above, plus
2nd time also Clear Data. Start F-Droid, choose repos, swipe down for refresh. Install app.

If that doesn’t work, repeat above, except restart phone before starting F-Droid.

There is F-Droid Version 1.10-alpha0 you could try. But sounds like you would have to download the APK from this page:

to

https://f-droid.org/repo/org.fdroid.fdroid_1010000.apk

but this method is not standard.

Edit: I’m ASSuming in aegis_25.apk the 25 is a typo because 35, 36 and 39 are available now.