Footnotes save to public, unprefixed "footnotes" field

[Milber]

We use a custom solution for adding footnotes to posts. All of our posts with footnotes became uneditable after WP's own implementation for footnotes was introduced. When trying to edit a post with "our" footnotes, the editor throws a JS error "i.map is not a function" for this line in core-data.min.js

i = t.footnotes ? JSON.parse(t.footnotes) : [];
if (i.map((e => e.id)).join('') === r.join('')) return n;

Posts containing footnotes do not save or update anymore. We believe this is because WP footnotes are saved to a public, unprefixed meta field "footnotes" (see wp-includes\blocks\footnotes.php, 70), which conflicts with our own custom footnotes implementation, which already uses the exact same field name.