OpenSearch was removed in the 2019 Firefox for Android remake and still not brought back. Just look at the steps one needs to take to add a search engine now — this is not normal. It also makes engines other than the default ones second-class citizens, without even their own icons.
Tap the three-dot menu button.
Tap Settings.
In the General section, tap Search.
Tap Add search engine.
A list of additional predefined search engines will be displayed.
Tap the Other radio button to add a search engine and do the following:
in the Name field, enter Kagi.
In the Search string to use field, enter https://kagi.com/search?q=%s
In the Search suggestion API (optional) field, enter https://kagi.com/api/autosuggest?q=%s
Tap the confirmation button in the top right corner of the screen.
If your browser is configured to default to private browsing, this will require you to log back in to Kagi each time your tabs are closed. To get around this, in the Search string to use field, use your session link and append &q=%s at the end.
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