As far as changing the certs, I know offhand to do it with a couple random linux distro's but i'm not 100% sure for android, you might just try searching the repo for the default certs then looking at how they are built into the image and tweaking that.
But for beginners there are some pretty nice LineageOs build guides floating around:
For specific pieces of hardware: https://wiki.lineageos.org/build_guides.html
Generic instructions: https://forum.xda-developers.com/chef-central/android/how-to...
As far as changing the certs, I know offhand to do it with a couple random linux distro's but i'm not 100% sure for android, you might just try searching the repo for the default certs then looking at how they are built into the image and tweaking that.