In Ubuntu by default you see the snap package and I think snaps are handled by Nextcloud “officially” by themselves, so I think/hope it gets updated in snapstore soon.
In Mint you’ll see the flatpak package of the Nextcloud client, which is maintained by the Flathub maintainers. It seems that they are on it but have to wait for some other dependencies in the flatpak ecosystem to be there/updated for NC client 2.5.x. (see: https://github.com/flathub/org.nextcloud.Nextcloud/issues)
Please keep in mind, that the ppa contains the system’s binary (.deb) version of the Nextcloud client and it seems you’ve used the snap/flatpak version so far. Including the ppa and installing/using its NC client version is like using another NC client app. You could technically use the old one and the new one side by side, though not recommended because with NC you have the communication with the server as well. When starting the new one from the ppa (for the first time), you will see that it is like a fresh installed version. You either have to manually transfer your settings from the flatpak/snap version to the .deb version or do the setup of your accounts and syncs in the new client again. If you decide to use the ppa version in future, I would save my old client configs, remove the snap/flatpak version of NC client and install the one from the ppa and transfer the configs or do a new config.
So you have two possibilities:
Wait for the update in snapstore and flathub and use the “old” but stable 2.3.3 version in the meantime.
Or if you really need the new features of 2.5.x now, use the ppa version. The ppa seems to get faster updates than snapstore and flathub.