If you do small scale (we're talking self-hosted git here after all), all these are either non-issue or a one-time issue.
Figuring out backups and firewall is the latter. Once figured out, you don't worry about that at all. Figuring these out isn't rocket science either.
As for the former. For minimum maintenance, I often run services in docker containers - one service (as in compose stack) per Debian VM. This makes OS upgrades very stable and, given docker is the only "3rd-party" package, they are very unlikely to break the system. That allows to set unattended-upgrades to upgrade everything.
With this approach most of the maintenance comes from managing containers' versions. It's a good practice to use fixed containers' versions which does mean there is some labor involved when it comes to upgrading them, but you don't always have to stick to the exact version. Many containers have tags for major versions and these are fairly safe to rely on for automatic upgrades. The manual part of the upgrades when a new major release comes out can be a really rare occasion.
If your services' containers don't do such versioning (GitLab and YouTrack are the examples of that), then you aren't as lucky, but bumping a version every few months or so shouldn't be too laborsome either.
Now, if DDoS is a concern, there is probably already the staff in place to deal with that. DDoS is mostly for popular public services to worry about, not for a private Gitea instance. Such pranks are costly to randomly poke around and require some actual incentive.
But why keep a private instance out in the open anyway? Put it behind a VPN and then you don't really have to account for security and upgrades as much.
I self-host gitea. It took maybe 5 minutes to set up on TrueNAS and even that was only because I wanted to set up different datasets so I could snapshot independently. I love it. I have privacy. Integrating into a backup strategy is quite easy —- it goes along with the rest of my off-site NAS backup without me needing to retain local clones on my desktop. And my CI runners are substantially faster than what I get through GitHub Actions.
The complexity and maintenance burden of self-hosting is way overblown. The benefits are often understated and the deficiencies of whatever hosted service left unaddressed.
LLMs don't store the code, only the probability chains of tokens (words). AFAIK this is not plagiarism.
I remember the later 2000s, when a German company called "Rocket Internet" was copycatting companies like AirBnB, Zappos and others. Many consider this lame and some kind of moral freeloading, it's not prohibited.
I'm sure if you used that big, smug brain of yours you'd piece together exactly what I meant. Here's a search query to get the juices flowing:
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
Whether you agree with why someone may be opting to self-host a git server is immaterial to why they've done so. Likewise, I'm not going to rehash the debate over fair use vs software licenses. Pretending like you don't understand why someone that published code under a copyleft license is displeased with it being locked in a proprietary model being used to build proprietary software is willful ignorance. But, again, it makes no difference whether you're right or they're right; no one is obligated to continue pushing open source code to GitHub or any other service.
A tool like this is not fundamentally more complex than a browser or a full-fledged IDE.
The only maintenance I have had to do was when the "I don't care about cookie's" extension got sold out, so had to switch to a fork [1]. That was 2-3 years ago.
[1] https://github.com/OhMyGuus/I-Still-Dont-Care-About-Cookies