(lineage-19.1-20220627-nightly-pro1-signed.zip on June 5 security patch installed smoothly using adb sideload and MindTheGapps-12.1.0-arm64-20220605_174313)
@pebert I would advice to factory reset. But as @Hook suggested try with a flash first, and if that does not fix it go for the reset. You are mentioning Magisk, and If I understand correctly, some things are principal different in that aspect going from 18 to 19.
(lineage-18.1-20220321-nightly-pro1-signed.zip on March 5 security patch installed smoothly using OTA )
...But the reintroduced (early August 2021) Accessibility / keyboard bug is not (yet?) fixed.
The stage after download and install called "Finalising package installation" is surprising slow though)