Permission to Install Apps from F-Droid on LineageOS 16

Hi, I’ve installed F-Droid in a fresh LineageOS 16.
Always when I try to install a app from F-Droid, I been lead to the dialog for allowing install from untrusted sources. But it’s set to ON, and after return to the install screen, the install will terminated.
How can I fix this?

Do you have any overlay/draw-over-apps app installed like Twilight, Redshift, CFLumen etc?

No.

For the moment, I’m only able to install apps by downloading the apk from fdroid and then install it via file browser.

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