What do you think about a LE 11 support for PI 5 ? Is it possible?
If yes, must we have to wait for a Kodi Nexus 20.3 release?
Kodi still has the intent to make a 20.3 release but there are complications with shipping another K20 Android release via the Google Play store as Google now requires a minimum API version that's higher than K20 implements (and each API bump typically requires some finessing in Kodi code). The route forwards hasn't been agreed yet.
If/when/once https://github.com/LibreELEC/LibreELEC.tv/pull/8181 is merged support will be in nightlies; although personally I'd still prefer the team to focus on an LE12 release; while LE11 compiles fine I'm not sure anyone put some testing miles on it and users expect "stable" releases to be, well, stable.