My main complain by far to LineageOS is the necessity to wipe everything for major releases on my S10. That's not possible every year.

What about Graphene ? Can I get 5 years of updates without needing to wipe the phone ?

Yes, GrapheneOS has always offered OTA updates via the System Updater app. https://grapheneos.org/usage#updates It's set up to download and install updates automatically by default. Alternatively, you can install a signed update package via adb sideload. https://grapheneos.org/usage#updates-sideloading

Both the update client and the backend are open source, just like the rest of the system: https://github.com/GrapheneOS/platform_packages_apps_Updater https://github.com/GrapheneOS/releases.grapheneos.org

> My main complain by far to LineageOS is the necessity to wipe everything for major releases on my S10. That's not possible every year.

Are you sure that you are not just misinterpreting the upgrade instructions?

For the S10 a mandatory wipe-on-upgrade has last been the case when upgrading from versions _older than LineageOS 21.0_.

During the time where LineageOS 20 was the current version there was no requirement to wipe listed at all, so presumably it didn't exist then.

You don't need to wipe the phone when updating GrapheneOS. It's as painless as on stock Pixel OS. OTAs downloaded and installed on the background, just reboot the phone after.