I had installed Megasync from AUR, and it was working until a recent update after which it will not autostart at boot. Running megasync from terminal I got
megasync: error while loading shared libraries: libssl.so.3: cannot open shared object file: No such file or directory
I uninstalled Megsync and downloaded the client from the Mega website, following the instructions sudo pacman -U Downloads/megasync-package, after which Megasync was working fine again.
However, the update manager in Pamac wants to upgrade Megasync, and if I do the libssl.so.3 error returns.
For now working around by ignoring the update.
EDIT 2022-11-27: After a while pamac started throwing error messages about the pgp signature of the package from mega.io. I uninstalled that and is currently on version 22.214.171.124 from AUR without any issues.
I got that is why ALA is disabled on the stable branch.
Installing packages from the ALA is inherently dangerous as sometimes Manjaro needs custom versions of certain packages. Doing this can result in a broken system. As a result, downgrading from the ALA is disabled by default on the stable branch. If needed, you can enable it by setting the environment variable
As this is a custom build script - you will have to wait for the maintainer to update the script or you can clone and modify yourself.
The package you can fetch from Megasync web is for Archlinux. If you want to sync a package like this you will have to be closer to Arch - e.g. switching to unstable branch - otherwise requirements may not be met.