For most add-ons, bundling dependencies at build time and modifying sys.path is enough (I have done that for dozens of add-ons), though that’s not practical for packages such as spacy.
It’s possible for Anki to bundle uv/pip with the new packaging tool, but dependencies have to be installed separately from Anki’s own dependencies, which are stored in a folder like site-packages but no full Python environment listing pinned dependencies, so we don’t get conflict resolution for free. Related: [Wiki] Bundling Python modules with add-ons - #4 by dae
I created an issue: Bundle uv/pip in Briefcase package? · Issue #5033 · ankitects/anki · GitHub