I've been working on this for a little over a year. It's called TuxTalk. You hold F8, talk, let go, and it types what you said into whatever window you're in. Everything runs on your own computer, nothing gets sent anywhere.
It used to be called TalkType. Turned out another company owns that name, so it got renamed a few days ago.
By default it uses the Parakeet speech model, which is fast even on the processor, and it can use your graphics card if you have one, AMD and Intel included. Whisper models are there too if you need more languages. I use it on KDE Plasma under Wayland, and it works on GNOME and X11 as well. There's an AppImage, a .deb and an .rpm, and it's on the AUR.
Full disclosure, I build camper vans for a living, so this is a hobby project. It's free and MIT licensed. What I'd really like is feedback, especially from anyone on a distro I haven't tested.
There's a short video on the site: https://ronb1964.github.io/TuxTalk
Code: https://github.com/ronb1964/TuxTalk
Questions or problems: https://github.com/ronb1964/TuxTalk/discussions