https://pairdrop.net is FOSS, cross platform, realtime, peer-to-peer, and only needs a browser. You can host your own version if you prefer. In contrast, Firefox Send (also FOSS) was 'asynchronous' (you could upload, and then email a link), but it was shut down due to abuse. https://github.com/timvisee/send is a fork of the archived github project that you can self host with many improvements, notably authentication, so only yourself and trusted users can upload. (edit: wrong link for ff send)
F-Droid
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
Matrix space | forum | IRC
curl --upload-file thefile.tgz https://transfer.sh/somename
Then paste the resulting URL to the person who wants the file. Another useful app is the magic wormhole and I think there are some web front-ends for it.
Proton drive gives you 1GB for free and you can share files using a link. They can view and download the files with the link, plus you can set it to expire and password protect it. You'd have to do starting deleting older files to share new ones, but 200GB is quite cheap if need be.
It sounds like you just want a generic file hosting website. Does it need to have an app on your end? At most, you need an account on that website to ensure your the only recipient. If you dont need that though something like mega should be fine.
I was looking for an app for file transfer using a local network(hotspot, wifi etc)
works on android, ios, macos, pc: localSend
needs the app installed, but it's the easiest I've found
with onionShare you can share with anybody who has tor browser installed through an url
Hmm. There's qrcp but thats desktop to mobile. Something like that for android....
Not sure if it's what you look for, but transfer.zip is a good website for P2P file sharing in my experience
I use sharedrop.io if the other device is connected to the same network. Just need a web browser, no need to install an app.
Also works across the internet by inputting your unique id.