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:
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.