OK, no problem. I deleted it.
Looking at the repo in detail it becomes clear that it is pretty large (1.1GB git files), but by no means the largest repo on Codeberg.org. The linux kernel source code mirror for example is about twice as large without causing problems in the Gitea UI: https://codeberg.org/mirror/git.kernel.org_pub_scm_linux_kernel_git_stable_linux.
Would you mind to keep the issue open so that we have a marker for further investigation?
Deleting a branch is permanent. It CANNOT be undone. Continue?