I personally got a lot of benefit from singing teachers who posted daily vocal warm-ups on Youtube that you can try and sing along to, and they tell you what to do and what not to do. Exercises to separately work on and develop your posture, airflow, vocal chord usage etc are useful as you can improve the individual parts. I'd never had any vocal training and am not trying to be amazing - just to improve and have some control and consistency.
Some also post classes, where you can see them coaching others and learn from them.
Listening to podcasts by performers about their daily routine might be useful if you want to know what they need to do to care for their voice in order to be able to perform daily.
Particularly I'd mention Eric Arcenaux: https://www.youtube.com/watch?v=Q5hS7eukUbQ
Listening to podcasts by performers about their daily routine might be useful if you want to know what they need to do to care for their voice in order to be able to perform daily.