After software support for OnePlus 5T ran out 2 years ago, we spent a LOT of time getting OnePlus 5 and 5T up to speed on LineageOS. By now it is safe to say that LineageOS on these devices is superior to OxygenOS, especially in terms of performance and battery usage. We ported over EAS (energy aware scheduling), fixed tons of big and small errors so now everything is working smoothly. The latest official version is based on Android 12, but the version for Android 13 is in an even better state already, so it will be released rather soon!
Also, some legacy devices got some much needed love, such as Sony Xperia Tablet Z2 WiFi and LTE variants. Both of them are now running LineageOS 18.1 based on Android 11 just fine.
Go check it all out at the LineageOS Download Center.
I would like to take this opportunity to thank all the donors who donated money and in some cases even devices for me to help improve the situation. Your help is very much appreciated, and you guys are all in the Hall of Fame!