I found the image on Mastodon, so it's not mine, but I agree. I never let my battery get below 50% if I can help it. If it gets below 20, I'm in panic mode.
Modern Lithium-Ion batteries like to stay between like 40%-70% charge, and going above or below that wears of out a bit faster. It was older batteries where you needed to fully empty and fully charge them.
Most modern devices can manage the battery for you pretty well, helping with any harm it might do. But even then, it’s less bad for the battery than deep discharges and recharges (where the battery does get low). It’s honestly probably fine.