I do lots of work on my phone thanks to Termux and a 60% bluetooth mechanical keyboard. It's one of my most essential apps on Android. Either using it directly or using it to SSH into servers, raspberry pis, etc.
I use an RK61 one from Amazon[0]. Haven't had any problems with it. I use it quite regularly for my phone and some RasPis. I made a little bracket to hold my phone at the top of the keyboard so I can sit with it on my lap or a table and type for extended periods quite happily.
I use my phone as my primary mobile computer (I don't own a laptop anymore) and am very happy with this setup.
He probably meant hardware keyboard. <strike>I don’t think anyone makes Bluetooth mechanical keyboards.</strike>
Ok I’m apparently totally wrong about that last thing and possibly the first as well.
Actually there are many. I've been using this one [0] for around 2 years, with blue switches. Despite some bad reviews, I don't have any issue with it. It can be paired with up to 3 devices + wired USB, so I can swap from phone to desktop to media center with 2 keypresses.