On rooted phones that don't have TWRP, how can you "start from fresh" with reflashing stock ROM?

I have stock Android 16 with root. It's become buggy in various ways, like LSposed stopped working. I think the easiest way forward is to reflash the factory image from the manufacturer's website. What's the easiest way to do this while maintaining my data, like text messages? I would like root again. My phone doesn't have custom recoveries like TWRP. I guess I could backup everything using neo, flash the phone, root it, and restore from the backups. But this seems like a lot of work and may be error prone. Is there a better way?