I need a distro which is package-agnostic since i use a lot of old ooen source academic software and they alternate between being only supported on RHEL or Ubuntu
Perhaps you should look into container solutions like e.g. Distrobox. You can basically install/run any package; just ensure usage of the correct container environment.
Fedora 39 is great except when i need to build the above mentioned software from source and i spend 2 hrs failing to match the dependencies from Ubuntu
If you’re otherwise content with Fedora, then perhaps consider installing the aforementioned Distrobox; which happens to be found within Fedora’s repos and thus one sudo dnf install distrobox away from being installed on your machine.
Also want to improvey laptop’s battery life, but i think i can’t get it much better than in Fedora
I’d argue that Fedora is not best for battery life, though. Minimalist distros tend to be a lot better at this. Installing auto-cpufreq in Fedora Silverblue on my AMD-powered laptop did come with significant improvements, so perhaps you could prolong your battery life by utilizing it or similar programs; think of TLP, thermald etc to name a few.