This website has wonderful resources for how to approach toddler meltdowns:
https://ourmamavillage.com
I haven't taken any of the courses, but follow the therapist who runs it on Instagram and have gotten tons of tips and resources. You can download a PDF specifically about toddler meltdowns at the link above. I've shared it with every toddler parent I know, it's so good.
This is also good, and has some resources available for free in addition to the courses they offer. The child development expert who runs it hosts weekly live chats on Instagram that I have found very helpful as well:
https://seed-sew-llc.mykajabi.com
I also liked the books Happiest Toddler on the Block and The Danish Way of Parenting.
Good luck!