One of the reasons I still use github is that I have starred quite a lot of projects and had to make an account initially to star a project. (I used to have bookmarks beforehand but I wanted to support author in a minor way :] and also github being de-facto & I wanted to talk to some projects which had issues which I wanted to create/discuss)
Another minor point is that Github actions are more generous than Codeberg's actions equivalent.
I believe hosting own Codeberg ie. Forejo (which is a gitea fork)/ gitea is actually easy. I once hosted them on my android phone using termux and on servers. Really liked the idea of having essentially github at my pockets.
For Gists [which is something that I like using a lot personally]. I found the idea of opengists really interesting as well. one minor complaint with opengists is that I love the comment part of gists which is an open issue in opengists but its not implemented yet. Wish it could be implemented.
Regarding losing bookmarks, I actually have a custom tampermonkey script in a private gist which shows a star button which essentially moves my bookmarks to some gist in a json format so as to not lose them ever again essentially.