Get a NAS for home, and VPN in as needed. Store all your media on the NAS, and also use it as a phone backup target.

Bluetooth is probably too slow for what you want, but you could use your old phone as a Wifi hotspot and even install various server software on it via Termux.

Get MaterialFiles and turn on sftp server to share all your files via network.

Then same network whether its hotspot or home WiFi.

Some travel routers have a USB socket for media.

They're usually used to make connecting to hotel Wi-Fi easier (you connect your devices to its ssid, then connect to its admin page and connect it to the wifi, or just plug it in to the lan).

Tp-link ac750, for example

https://www.tp-link.com/us/support/faq/340/

If you're looking for something you can carry about and use to store data on, why not just a USB-C thumb drive or external SSD?

Edit; this is intended for photographers, but you can get external SSDs that create their own WiFi network so you can transfer files wiressly to and from them: https://www.westerndigital.com/en-gb/products/portable-drives/wd-my-passport-wireless-ssd?sku=WDBAMJ2500AGY-EESN

That's a neat idea of using an extra phone as a file server. I've only thought of phones as consumers, not providers.

Maybe be more specific?

For traveling I would suggest a laptop to behave as a server but the IP address changes a lot when traveling.

I'd personally opt for something hosted at home if possible like Nextcloud and Jellyfin with static IP and port forwarding to access on the go.

Tbh though, if you just want storage on the go buying a portable 1-4TB drive that connects via USB-C is enough.

This seems a bit impractical. 2 phones to keep charged and manage.

Depending in your use case can't you just get some external USB storage?

If you don't have concerns about it being private I've used one of these for similar purposes in the past. Just a little portable DLNA server. The original project stopped but there are forks or the last version of the original out there.

https://en.m.wikipedia.org/wiki/PirateBox

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

4 acronyms in this thread; the most compressed thread commented on today has 6 acronyms.

[Thread #680 for this sub, first seen 15th Apr 2024, 08:55] [FAQ] [Full list] [Contact] [Source code]

Just saw the edit and if you don't want to go the router route + LAN for some reason guess another option would be a ucb c dock that allows power pass through. I have an anker one that I use on occasion and recommend it. You can then either get an external drive or a SD card.

Does it have support for microSD cards?