Hi ...
I'm running boinc since 10 years now without problems and actually I'm running it on fedora 40.
On Fri 14 Jun 2024, "Discover" upgrade boinc-client and boinc-manager to 8.1.0-770 and I found this was normal.
But, since this upgrade, EACH DAY "Discover" find a new one ...
The last one, today, is :

Begin time : Sat 06 Jul 2024 11:45:12 AM CEST
Upgrade boinc-client-8.1.0-821.x86_64 @boinc.berkeley.edu_dl_linux_nightly_fc40
Upgrade boinc-manager-8.1.0-821.x86_64 @boinc.berkeley.edu_dl_linux_nightly_fc40

For me, this seems to be strange, and I ask myself a question: Is it "normal" ?

It is because you have set it to upgrade from Nightly branch instead of Stable or Alpha.
https://boinc.berkeley.edu/linux_install.php

So evident ... Sorry :o(
I think that, just changing the repo is not enough to switch to a Stable version ...
So, If I reinstall with the Stable or Alpha version, do I loose my configuration and all the work done ?

So, If I reinstall with the Stable or Alpha version, do I loose my configuration and all the work done ?

No you can swap between versions without affecting work or configuration. The only time this changes is if you use the flatpack or possibly with compiling your own from scratch. With the latter you can choose where it goes.