Guide for Linux: https://strict3443.codeberg.page/i2p-info/hugo/public/posts/how-to-use-i2p-on-qbittorrent-nox/

You can install i2pd with sudo apt install i2pd and then point your services towards your i2p router (Ex. 127.0.0.1) and you are good to go.

You can try using BiglyBT on android following these instructions: https://github.com/BiglySoftware/BiglyBT/wiki/I2P#user-content-biglybt-i2p-and-android

Otherwise, I’d suggest using a desktop to run i2psnark, BiglyBT, or qBittorrent and use i2pd along with those clients.

Yes, absolutely. I have a VPS that runs a i2pd router and I can set my clients to point to my VPS and I am able to use the I2P network. In doing so, I had to make sure I forwarded the correct ports on my VPS so that it would reach the i2pd application. I will do a write up soon.

Yes, I did exactly this when I2P support was first in beta. I have a docker stack with Gluetun as my network for all my *arr containers and I was able to still point my qBittorrent to my i2pd router and it worked just fine.