Is there any good data on blockchain state growth? 

Want to understand how many megabytes or gigabytes per day are being added to full nodes in Eth, Solana etc.

Technowatermelon. Elder Millenial. Building Farcaster. 

nf.td/varun

For Ethereum, the chain is growing around 100-150 GB per year, so roughly 300-400 MB/day. Solana's growth varies, often adding several gigabytes daily due to its higher throughput. Tools like Etherscan or Chainz offer insights. Chain-specific explorers or analytics sites will provide detailed, up-to-date stats.