AbsolutelyNotCats

I agree it’s good but maybe OP wants an open source alternative

How do I get rid of the annoying prompt at the top of the app?

Using any unofficial client like Nekogram

I’m thrilled to see companies shifting to Mastodon from Twitter. Mastodon’s decentralized nature and open-source foundation provide a healthier and more meaningful online experience compared to Twitter’s chaotic, ad-driven environment, specially after elon turd bought it

You must use the company Wi-Fi then you must use a VPN

The company VPN or the client VPN, sadly