Oh it's been ages since I was reading into LineageOS. Need to look into it again. If the original OnePlus still gets updates this way this should be a piece of cake :)

Still rockin' my OnePlus 6T. Have it since about 4.5-5 years and I don't at all feel the need to change something about it. Battery life is still alright. Only thing that makes me sad is it doesn't receive any more updates, not even the security patches :-(