[planckscnst]

If you like this tool, you might also be interested in reptyr, which lets you reparent a process to a different tty.

https://blog.nelhage.com/2011/02/changing-ctty/

[ranger_danger]

and some other tools similar to reptyr:

https://github.com/jerome-pouiller/reredirect/

https://github.com/pasky/retty

https://github.com/trishume/telefork

[jauntywundrkind]

Tried 3/4 of the tools, and none helped me reattach neovim.

Ended up using dtach. Needs to be run ahead of time, but very direct and minimal stdin/stdout piping tool that's worked great with everything I've thrown at it. https://github.com/crigler/dtach

[ranger_danger]

have you tried diss, shpool or abduco?

also vmux appears to be specifically tailored to vim/neovim

https://github.com/yazgoo/vmux