Currently, the goUP command behaves unaware of page anchors (#xxx), query strings (?xxx), and sub-domains (xxx.). When first using goUP command, anchor and query is removed at along with the last part of the directory. And after using the last goUP command, sub-domains are not removed and it stays on the same URL. Lack of these features is the primary reason why I still keep the separate NavigUp extension around:

Navigate to parent address. It means removing page anchor (#xxx), query string (?xxx), file or the last directory (/xxx), port number (:xxx), sub-domain (xxx.) or secure layer (https -> http), whichever is first found (preserving mentioned order).

Removing the secure layer (https -> http) is probably unnecessary in 2021 (the extension is from 2013), but the rest I find very useful. For when you actually want to remove the achors and queries at once, the extension has additional shortcuts:

Use Alt+Up (Shift = +1, Ctrl = +2 levels) or click the icon (many times = many levels).
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Use (Ctrl+)(Shift+)Alt+Up for it. Shift means going up one more level, Ctrl - additional two levels. Ctrl and Shift can be combined. If you click extension's icon (in the address bar) many times within one third of second, then you'll go up many levels at once.

Vimium already has this implemented in a more intuitive way (number and then the goUP command shortcut), so I would love to use that instead, if goUP is able to navigate in more parts of the URL like the NavigUp extension.

In the meanwhile, I think the goToRoot command should probably stay as it is, without stripping the subdomain, as stripping the subdomain would be achievable with a subsequent goUP command if desired.

(A portion of this potential feature was previously mentioned by one of the maintainers in #1344.)