I am thinking about setting up a local HTTP web server with something and HTTP proxy to share my VPN connection easily. But to be honest I am also kinda lazy. Ok, alot.
Maybe NGINX for web server and Privoxy for the proxy server. Or tinyproxy. I don't know to be honest. When I'll have too much extra time at school I can look into that.
Anyway, there's also ffmpeg. Pretty useful.
And since you can run GUI in it, noaa-apt for decoding APT imagery from the last NOAA satellites still broadcasting APT at 137MHz. (NOAA-15, 18 and 19. NOAA-15 currently has broken AVHRR scan motor, but it's not the first time.)
Termux yeah. I use it everyday. So here is a (long) list
Use ffmpeg to convert videos or even edit it(with current 6.x version, mediacoded hwaccel is availiable)
yt-dlp
Use vim and emacs, maybe code something
Integrate it with other plugin apps like Termux:API(lots of system apis), Termux:Boot, Termux:Float(floating terminal), Termux:Widget, even Termux:X11 For running gui apps
You can run gui apps with other X servers like XSDL
Compile and run programs that is not availiable for arm(Worst thing, but i still does it. Much hassle and error prone, but fine for smaller programs)
Use ssh to connect to other devices
Install x11-repo and thus install xfce and firefox desktop(for fun)
Install proot-distro and use distros like debian, arch, ubuntu, manjaro, void, fedora, etc. which is cli only by default but you can install any DE.(You can combine display server from XSDL)
Use git, clone a repo, make changes, use it or push commit, whatever you do with git
Use your normal standard linux commands to browse thru your filesystem and make changes
neofetch, cpufetch, rxfetch, htop, gotop, cmatrix and hollywood for lolz
tmux, byobu or gnu screen
Tar, gzip and all coreutils
cryptomining(DON'T do that)
Test your webpage locally (php -S localhost:port)
Ahem I wasted a lot of time making this list i think i have to go now lol
Definitely try running a full Linux distro with it, it's pretty fun and a self-rewarding task, even if you don't end up actually doing anything with it. But you may still find it useful in some ways, for instance, you could run a full fledged desktop Firefox with support for ALL addons, use it to inspect and debug web pages etc.
And if you feel like it you could take it a step further and install Zink and Box86 to play Windows games.
I ssh into my desktop and do a watch sensors while I'm gaming, sometimes. Then I can make sure temps are good without taking screen real estate with mangohud or similar.
It may be broken or not work on some APKs, getting it running on Termux is kinda weird, but you could then use a better output of APKSigner to read signatures and verify APKs on first install.
Apksigner on its own was pretty useless for me, thats why it uses a workaround. Apks are zips, so it renames the file, decompresses and reads some file where the signer is actually mentioned with Name and all. Then it deletes it.
Iirc there was some bug with Termux and the unpack thing, because Android sucks I guess. On Linux it works fine.
@SaltyIceteaMaker I installed miniflux, a rss reader, on it. Sadly android constantly kills the internet connecting when the screen turns off, so I can't use it as a server to access it from my other devices. I have tried everything I could find to prevent that from happening.
@SaltyIceteaMaker I think you can use bash scripts and combine that with termux-widget addon to do some amazing stuff. I wrote a script around ytfzf to search and download YouTube videos using termux-dialog addon.