Data about number of block mined + stale blocks per day in Bitcoin? I am wondering if there is any easy way to get number of mined blocks per day + number of stale blocks per day for the last three month e.g.,?
I could not find such data on Blockchain.info

In Ethereum, however, Etherscan provides these, see: https://etherscan.io/chart/blocks and https://etherscan.io/chart/uncles

Any help about getting such data for Bitcoin?
To my knowledge, there is no high quality data source for this.

Blocks mined is fairly simple to check, as that is simply the main chain's progress.

Stale blocks is harder for Bitcoin and Bitcoin based currencies. Unlikely ethereum's uncles, references to stale blocks are not stored anywhere, and after a better chain exists, propagation will not take place, so many nodes do not see a stale block at all. The only way to collect data would be to run multiple nodes, connected to as many different peers are possible, and monitor the logs for chain tip reorganizations. As far as I'm aware, no one is currently doing this, and if they are it is not offered as a publicly available dataset.