My suggestion would be an airmouse remote, possibly with an built-in keyboard. This is because sooner or later you will want to use a web browser to stream content, and a mouse is incredibly convenient for that.

There are many bluetooth remotes you can use for this. You may want one that has a built-in keyboard, or just one with arrows and a handful of buttons.

This is listed on the linked page. KDE makes the excellent KDE Connect. You can also use a TV remote, game controller, or keyboard and mouse.

I use kde connect with my android for my htpc. Works nicely enough on stoxk kde.

Unified Remote with my phone https://www.unifiedremote.com/