Unified state shouldn't be much of a problem for static web hosting.
EarMaster
I use tt-rss in combination with FeedMe on my Android.
But what if your name is not Ian...
I think you have realized that every comment here was about your decision not to use Git. I don't think there is much more to say about this...
You don't have to. Absolutely not.
But: As a potential user it provides some additional features your solution lacks. I can easily fork or clone your repo and change things if I need to. If I think it benefits the project I can easily offer these changes back to you, if I don't I can still profit from future development on your side and incorporate my changes into it. I can very easily check what has changed between two versions without relying (trusting) your changelogs or performing a manual diff.
But most importantly it is a matter of trust. Not so much trust in your intentions and the possibility of malicious code (Git won't prevent that), but it obfuscates your code unnecessarily making it harder to continue if you at some point decide to stop maintaining it or even detect vulnerabilities as it is not easily accessible without knowing where to look for it.
Some BIOS manufacturers allow you to disable all halts on errors. As soon as you connect to the network your system should be able to sync its internal clock.
I like the idea, but may I ask why you don't use a version control system like Git (or anything else that fits your needs)?
Well, that escalated quickly...
I think the real question is not if it's possible (it is), but what you are actually trying to achieve. It seems like you have this idea, but I'm not sure if you really understand what it means. Maybe you can describe, why you want to host a Lemmy instance yourself...
There are use cases for battery trains. In remote, mountainous locations where the cost for electrifying a track is very high it is not uncommon to use electric trains with batteries. Here in Germany we have several regions where diesel trains have been replaced by them.
Discourse exists and is free to self-host and open source. Compared to classic forum software (like most *bb variants) it is a pleasure to use and feels not like a remnant of a lost age.
The (only?) downside is the similar name to Discord, but that's not them to blame, because they had their name first.
I'm pretty sure pentagons are a subspecies of bestagons...