Best way is to flash your self over the years maintained and evolved backup image. But since there are so many bugs and so many ways to fix a bug depending on your needs everyone has his own version.

My use (until the end of 3g) was

For browsing i used a server which i connected to via vnc or streaming.

location you could get to work but it is a total mess. My solution was to overwrite /etc/hosts everytime i connected to the internet to add an entry to supl.google.com to skip certificate errors.

functional:

leste is nice but even they seem to target newer devices.
Powermanagement wasnt/(isnt?) as good as on stock. Combined with a small battery you wont get far. But still your best choice.
But to run new software like maps or a browser on a device with 4GBit of ram will be hard. I had navit running for offline navigation, but if i rembered correctly i had my own version which had less bugs but still had a ton of bugs and was slow as hell cause it could not use location and sdl at the same time. There was a huge patch for it for the similar palm pre but (luckily) it didnt survived the time.

stock
Stock uses a lot of things that arent used anymore, in ancient (highly) modified versions.
If you want to learn how to not do it: this is your way forward

for me it is not functional as a phone or computer anymore and not worth the trouble.

It is still a nice device for tinkering with all its sensors, connectivity, battery, small form factor, ok documentation and a (mostly) helpful community.

But devices are harder to get and too expensive to justify all the learning about all the hardware [resolder usb port] and software bugs.