Hello again; I kept thinking about this, because I had something similar in the days I was forced to use Windows at work (TextEditorAnywhere), and decided I missed it too much on GNU/Linux not to figure something out.
I call it vixf ($VISUAL X11 field). It's supposed to be called via hotkey from a window manager or sxhkd. Screencast attached.
It seems to install with pipx. On GNU/Linux, you need to install xclip(1) too.
I wrote a wrapper for the OpenSSH client to downgrade the sent TERM strings for IPv4/IPv6 hostnames or hostnames matching a set of patterns, which network gear CLIs are more likely to accommodate.
Newer OpenSSH can send a TERM string per-host with ssh_config(5) files, but I wanted something that adapted to the outer terminal: tmux-256color→screen, xterm256-color→xterm, etc.
This came up because newer versions of tmux set their own TERM type now by default.
With my first FOSDEM done, I'm leaving continental Europe shortly, and returning to New Zealand in a few days. I've had a great time, and am grateful for everyone's company and help, especially @kline . Thank you!