Since 7.3 and the fix for bug 142763, we can separate the first page footer or header from the rest in Calc, thanks to the new "Same content on first page" setting in Format > Page Style > Footer or Header. In the help pages for "Format > Page Style > Footer > Edit"[1] and "Format > Page Style > Footer > Edit"[1], there is no mention of the conditional "Footer (first)" and "Footer (rest)" tabs. Visibility of those tabs depends on the Page style's footer setting "Same content on first page".
(published before finishing, here's the full description) Since 7.3 and the fix for bug 142763, we can separate the first page footer or header from the rest in Calc, thanks to the new "Same content on first page" setting in Format > Page Style > Footer or Header. In the help page for "Format > Page Style > Footer/Header > Edit"[1] (same for both), there is no mention of the conditional "Footer (first)" and "Footer (rest)" tabs. Happy to take if no objection. [1]: https://help.libreoffice.org/24.8/en-US/text/scalc/01/02120100
(noting that this report was inspired by the users' confusion in bug 153997 and bug 159782)
Stéphane Guillou committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/fcf19e4c9105e8e1a4d4523fc108ff2f957f2023 related tdf#160057: fix dead link to Edit Footer/Header
Stéphane Guillou committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/04dcd1b951689689f9449408fd6f512a9c87aa0d related tdf#160057: replace last ref to defunct Footer Header page
Stéphane Guillou committed a patch related to this issue. It has been pushed to "libreoffice-24-2": https://git.libreoffice.org/help/commit/9bed20d260f9c0dfd5a43f62bba288aff829da85 related tdf#160057: replace ref to obsolete Footer Header page