I have spent a lot of time playing GB/GBA games and Advance Wars is among my favorites. I love the "hot potato" mode for playing with a friend with just one device.
Python / FastAPI will be better than Java in your situation and is easy to learn. Go should be even better and is also relatively easy to learn!
I own two Raspberries 1, a Raspberry 4 8GB and a Raspberry 5 8GB. I wouldn't recommend the 4 as a full-fledged desktop replacement, but the 5 has been very smooth so far.
I'm currently using the latest Raspberry Pi OS Lite and installed KDE on top.
I was lucky then with the 4 A400 I'm still using. I also have 3 BX500 that have been very reliable.
Kingston A400s and Crucial BXs have been very good as cheap SSDs in my experience.
A VPN would be my first choice. ZeroTier works like a charm on the RPis. I've shared even SQLite databases over Samba over Zerotier among a bunch of RPis daily for a couple of years without a hitch.
My own example. I still have an ancient netbook lying around. It runs on an Intel Atom N270, which is only 32bit / i386. It came with Windows XP and I quickly switched to Mint, when it was still supporting 32bit.
I think the last Ubuntu release supporting i386 was 18.04 (around 2018) and all other distros started to drop i386 support after that.
AFAIK Debian is the only major distro still fully supporting i386. And a Debian based distro that still supports i386 is MX Linux. My ancient and crappy netbook is running MX Linux right now.
My 'weird' example. I have a Raspberry 5! It's ARM and very new. It runs its own distro, Raspberry Pi OS (Debian based), and Ubuntu does also fully support it. Right now if you try some other distro, it probably won't even boot unless you start tinkering a lot with it.
So Debian is definitively a choice for very old hardware. And the odd ARM SoC has usually at least some custom Ubuntu build that runs with it.
Same problem here!
TalkPython episode about Memray: https://talkpython.fm/episodes/show/425/memray-the-endgame-python-memory-profiler
PyQT / PySide are huge, but they have been very good in my experience coding cross platform desktop programs. macOS, Windows and Linux (even on ARM) are very well supported.
I use VSCode for coding, but if it's a small script or pure text files, then I use Geany.
Python 3.14 Release Schedule: https://peps.python.org/pep-0745/