Sweet…
I created the squeekboard/keyboards path in .local/share, then downloaded this file: https://source.puri.sm/Librem5/squeekboard/-/blob/master/data/keyboards/terminal/us.yaml`, placing it in my keyboards directory. (It’s labeled “us,” but it’s actually terminal layout.)
Everything now defaults to terminal-style keyboard, although it still shows English (US) as selected, just like it already showed by default when opening Terminal, even though the layout is obviously “Terminal.”
Thanks for the tip,@uzanto.
EDIT: FYI, the L5’s original English (US) (*) keyboard won’t be available for use while the above version exists within .local, if that’s a concern. But you could always just remove the personal version, or temporarily rename it, if you want to revert to the original.
(*) …or whichever language your default keyboard version uses
EDIT, AGAIN: I just realized that you also need to add us_wide.yaml (in addition to us.yaml) to .local/share/squeekboard/keyboards, if you want the terminal-style board in landscape view as well.
(Meaning the us.yaml and us_wide.yaml files that the contributor uploaded as terminal-style versions in data/keyboards/terminal at https://source.puri.sm/Librem5/squeekboard/-/blob/master/data/keyboards/terminal/fr_wide.yaml )