I am sorry for not responding quicker, but I was at school and I am also tired, so don't expect a high quality reply.

Is this good or bad for Termux? I’m kinda inclined to think it is good (I have a SD 865 so I’m extra curious).

I have no idea. My phone and laptop are the 2 only pieces of hardware to test with. I also wanted to try OnWorks, but getting the file to that seems fairly painful. Downloading that particular video from archive.org is too slow, trying to get it from FileNow where I uploaded it would hang every 14MB and fail. The only working "solution" was running nginx webserver with that file there in Termux and creating Cloudflare QuickTunnel, but my mobile data is slow and we don't have internet at home. So I just didn't get to try it.

I have read about the self hosting possibilities before for sure and while I will always find it amazing I would die inside if I had to use my phone (and specifically Termux, since I think text selection, copy/paste and overall typing is bad on it), that without proper hardware ofc (like external mouse and keyboard… Or a UI like DeX) so I gotta ask, do you use any of those services? If yes do you have some of those tools I just mentioned?

I have only tried Jellyfin briefly and want to try running NextCloud when I'll have time for it, as that seems more painful looking at the guides on internet. Jellyfin just didn't fit my use case, so I replaced it for nginx with fancyindex module and Material theme.
I don't have a problem using the touchscreen. Copy-paste works pretty well, like with any other text. Just a little tip: Home puts you on start of the line and End at its end.
But anyway, I do often use a hardware keyboard. Sort of. I don't attach it to my phone, instead I SSH into my phone from some computer, be it my laptop or school PC. For GUI I can also use VNC server. Keep in mind VNC isn't encrypted by default. There's VNC-TLS and X509, but I have no idea how to deal with certificates, which allows anyone to do MITM attack on me. Simplest solution is running it over SSH tunnel, at which point I can use unencrypted VNC which is compatible with more programs.

I kinda want to know what you meant here.

RTL-SDR is one of the SDRs (Software Defined Radio) that I have. I also have a clone of RSP1. I don't know where I would start on that. It allows a lot. But after all, you can just search "What to do with SDR" yourself, and find countless answers.
My most favorite use is receiving satellite signals. So far only in the 137MHz band because I don't have a satellite dish. In this case V-Dipole is enough. Since I have the RTL-SDR Blog's extendable dipole, I can fit a satellite imagery receiving station into my pocket.
Check !amateursatellites@lemmy.world
Example image that I received over APT (it's analog signal, old-school tech):

I used noaa-apt, again in Termux, to decode it.
Or perhaps this catches your interest: Cracking GSM phone calls and SMS with SDR (YouTube playlist) which is obviously illegal. It also only works for the weak A5/1 encryption and only with GSM (2G). While newer standards are sure safer, don't trust anything that's not E2EE at all anyway.

I only know SDR from the video format scene, and I know you want HDR or better.

Yep, SDR = Software Defined Radio.

This is cool, and I didn’t know about it, but surely there are better options to use torrent on Android?

I am not sure. LibreTorrent works well for me.

I kinda want to know what more, because honestly, if Termux was paid you would almost sell it to me 🤣

I meant other FOSS apps, not stuff in Termux. But it's like a locked down GNU+Linux machine, so it just does a lot of Linux things. Thanks to proot-distro or Andronix scripts you can even have Ubuntu, Arch Linux or other distros on it. That's what you need for Jellyfin for example. Just keep in mind that your phone is most likely aarch64 and Termux doesn't emulate other architectures. Though it can run QEMU 😏 (but if you tried Limbo PC Emulator x86 you understand how useless it is with anything better than Windows 98). I did get that to run Windows 7, yes, but even just opening a file browser took a few minutes.
Anyway, cursed screenshot as a bonus:

Even though it CAN be done doesn't mean you SHOULD. I already cooked 1 Poco X3 Pro motherboard to its death.