Many thanks, Nicolas !!!
I've just tested. It looks good now. I should rather say it's excellent.

Am Mi., 6. Okt. 2021 um 16:13 Uhr schrieb Nicolas Goaziou <mail@nicolasgoaziou.fr>:
Hello,

Elias Bounatirou <elias.bounatirou@gmail.com> writes:

> However, it appears Nicolas' MWE unfortunately does not  reproduce the
> issue. It's not the footnote that is omitted/ not exported, it's the
> citation in the footnote that is left out (when the footnote follows two or
> more citations, of which one has a suffix). In Nicolas' MWE, there is no
> citation in the footnote. What seems to me (being no export on LaTeX)
> strange about Bruce's LaTeX output is that there is no command
> \footnote{...} or the like. So is the footnote-part of the LaTeX output
> real LaTeX? (Sorry for this naïve question.)

I noticed my ECM was not right. It took me a while to figure out the
issue.

> I've tested again.
> With verbose I get the same erroneous result: the citation in the footnote
> is not rendered (using the development version of org-mode, see below):
> INPUT:
>

[...]

> Body text [cite: @ravlic2021; @saric2010 with a SUFFIX][fn:1]

[...]

> [fn:1]Test [cite: @senker1987]
>
> LaTeX OUTPUT (shortened):
>
> Body text \autocites{ravlic2021}[][with a SUFFIX]{saric2010}\footnote{Test}

I think I fixed it. Could you confirm it?

Thank you.

Regards,
--
Nicolas Goaziou