[Nokia 6.1 (2018) Questions & Answers] MartJI.V.:
hello @chsiva, I would like to know if when installing the version of lineageOS 19.1 you used the lineageOS recovery, in my case I have reinstalled LineageOS 19.1 more than once without any problem. In fact, it is not so necessary to have the latest version of Android from the manufacturer installed to be able to install this version of lineageOS, I will explain the steps to be successful in the process.

1) Do not leave any custom recovery as permanent.

2) Since I have Windows 10, I had to look for the drivers that really work for Nokia, in which there are 2 drivers that are needed and apply some additional configurations to the main installer, one of them is compatibility with old versions of the operating system.

3) Download the tool that includes fastboot + adb and verify that the device is really recognized by the operating system regardless of the mode in which it is.

4) Being in the stock version, I recommend you to factory reset the device, then configure it.

5) Enter the download mode and through the cmd and in the adb mode use it to change the slot A/B (A or B), In both you will have to install the lineageOS recovery.

6) Having the recovery installed in both Slots (Remember to use Fastoboot to install the recovery) I recommend you to be in Slot B to proceed with the installation of the rom.

7) Then access the recovery, in my case I decided to perform a data format from the recovery and then select the ADB installation, I recommend you disconnect the device before accessing this option, when you access this option, connect the device to the computer (the recovery should indicate that you are in slot b before continuing with this).

8) Install the lineageOS rom and after it finishes, reboot the device and wait for it to boot.

9) When booting into lineageOS, apply settings and then reboot back into recovery mode.

10) Install the necessary Gapps to have the basic services of google, remember to be in slot b to continue, after installation, restart and when starting, connect to a network and configure.

11) The normal thing is that it is configured but in a partial way, the contacts that you have saved in your google account should not appear if you have it saved, if this happens, you only have to reset the device from the factory.

12) When starting again, apply the configuration connected to the network since the gapps are already included in the device, more configuration options should appear than the previous time when you installed the gapps and at the end the contacts should appear.

13) now if you can install magisk in version 25.2 if I'm not mistaken, remember to change the .apk to .zip and from the recovery install it from slot b and reboot.

14) and the last thing you need is to install 2 modules to certify the device with magisk (before this, I recommend you activate the option to hide root from applications, magisk should request a reboot, before rebooting, apply the deny settings of root to the applications that you deem convenient, but those of google if or if they have to be denied, in google services, mark all the options to deny root in its entirety).

15) For this procedure you will need a terminal and from the terminal, type the command (props), then press ENTER and sign the device.

16) and then delete data from play store and google services and then reboot the device and voila, your device is ready to use.

-In the event that you do not have a windows operating system, you can use the virtualbox tool and if it is possible to install the version of windows 7 ultimate, although you will have to install some necessary drivers so that you do not have a problem with the execution of applications from the virtualized system.