The instructions posted here in the Lineage OS web site regarding the update of oneplus do not work for me, I can't get the command
adb reboot sideload
to work, it simply reboots my phone.So these are the steps I took to update my phone to the latest version.
1. Restart phone in recovery mode:
power + volume down
(will also take screenshot, just wait) or
adb reboot recovery
2. In TRW select Advanced > ADB sideload > slide to start sideloading
3. Run command
adb sideload .\lineage-17.1-20200601-nightly-oneplus2-signed.zip
wait...takes some time, you should see progress indicator
4. In TRW select ADB sideload and run command
adb sideload .\open_gapps-arm64-10.0-nano-20200530.zip
5.Reboot.. Wait a long time