GrapheneOS only publishes updates for devices with active security updates. Your device is EOL and therefore won’t receive any further mainline updates. It still will receive extended support from the Android 14 legacy branch with whatever security patches arrive in upstream AOSP, but unlikely to see device-specific patches nor firmware patches. Your device isn’t getting the same care and attention that active devices are receiving nor will it receive any future versions of Android through GrapheneOS.

Before buying anything to supplement your hotspot, it may be worth checking to see if your issues are even caused by poor signal strength. Depending on the cause, buying better antennae or a signal booster relay may not provide any tangible benefit. As you say you live in a rural area, your issues may be unsolvable by different hardware as your device may be throttled by your carrier instead.

For what it’s worth, I do think OCIS is worthy of switching to if you don’t make use of all of the various apps Nextcloud can do. OCIS can hook into an online office provider, but doesn’t do much more than just the cloud storage as of right now.

That said, the cloud storage and UX performance is night and day between Nextcloud/Owncloud and OCIS. If you’re using a S3 provider as a storage backend, then you only need to ensure backups for the S3 objects and the small metadata volume the OCIS container needs in order to ensure file integrity.

Another thing to note about OCIS: it provides no at-rest encryption module unlike Nextcloud. If that’s important to your use case, either stick with Nextcloud or you will need to figure out how to roll your own.

I know that OCIS does intend to bring more features into the stack eventually (CalDAV, CardDAV, etc.). As it stands currently though, OCIS isn’t a behemoth that Nextcloud/Owncloud are, and the architecture, maintenance is more straightforward overall.

As for open-source: OCIS released and has still remained under Apache 2.0 for its entire lifespan thus far. If you don’t trust Owncloud over the drama that created Nextcloud, then I guess remain wary? Otherwise OCIS looks fine to use.