AlienBob recently updated his build of LibreOffice for Slackware from the -7 version to the -24 version, and my spreadsheets that used conditional formatting, created on -7.6, no longer display correctly. It's an upstream issue, since the App Image versions of -7.6 and -24.2 available from the LibreOffice website have the same problem. The internal format of conditional formatting has obviously changed, since the parsers and renderers in both UIs display the correct information, but the -24 version doesn't actually display the spreadsheet cells correctly. Re-entering the conditional formatting from scratch using the -24 UI works, and shift-ctr-v can be used to copy formatting between cell ranges in -24. The resulting spreadsheet displays correctly, and also displays correctly using the -7 App Image. I didn't try EDITING the new -24 spreadsheet with -7 App Image to see if that would break the formatting. So there is at least a forward migration bug in the "hidden" structure of conditional formatting.

I have some spreadsheets with fairly complex conditional formatting, and all open flawlessly in 24 - probably something else is the factor. I install binaries from the LO site. Anyhow, the proper place to report libreoffice bugs is https://bugs.documentfoundation.org/