I just did an upgrade from latest Lineage 18.1 -> to latest 19.1, following the stock instructions. After downloading the enchilada .zip file, and the MindTheGapps 12.1.0 .zip for arm64, I verified the checksums, and they were perfect.
When I actually did the install, I got a warning message that was a bit troubling, which was that the checksum failed for the MindTheGapps file (
as stated by the phone, in its Recovery mode) when I went to sideload it at the appropriate time, as per the
upgrade instructions. I went ahead and installed it anyway, knowing the checksum was OK as verified earlier after download.
The adb command itself reported no checksum error over on the laptop, from where the "adb sideload" command was launched.
Despite this warning, I went ahead anyway, and everything seems to have successfully installed (again, no complaint was seen from "adb sideload" on the laptop), and my enchilada seems successfully upgraded to Lineage 19.1.
Note: My security string (which is the important thing to me, which I'm most interested in when it comes to all such updates/upgrades) got bumped to "May 5, 2022", as seen in the phone's Settings -> About Phone -> Android Version -> Android security update