我在 Linux Mint 上安装了 texlive（版本 2023）。当我尝试使用tlmgr install sidecap 它安装包时，它提示我需要先更新 tlmgr。我使用了它，tlmgr update --self但它返回：
Unable to download the checksum of the remote TeX Live database,
but found a local copy, so using that.
You may want to try specifying an explicit or different CTAN mirror,
or maybe you need to specify proxy information if you're behind a firewall;
see the information and examples for the -repository option at
https://tug.org/texlive/doc/install-tl.html
(and in the output of install-tl --help).
tlmgr: package repository https://mirror.niser.ac.in/ctan/systems/texlive/tlnet (not verified: unknown)
[1/1, ??:??/??:??] update: texlive.infra [345k] (66512 -> 66822) ... TLPDB::_install_data: downloading did not succeed (download_file failed) for https://mirror.niser.ac.in/ctan/systems/texlive/tlnet/archive/texlive.infra.tar.xz
tlmgr: Installation of new version of texlive.infra failed, trying to unwind.
tlmgr: Restoring of old package did NOT succeed.
tlmgr: Error message from unpack: don't know how to unpack
tlmgr: Most likely repair: run tlmgr install texlive.infra and hope.
done
tlmgr: The file README has disappeared from the critical package texlive.infra but is still present in dehyph:texmf-dist/tex/generic/dehyph/README dvipdfmx:texmf-dist/fonts/cmap/dvipdfmx/README mfware:texmf-dist/mft/base/README texlive-scripts:texmf-dist/fonts/map/dvips/tetex/README
tlmgr: action update returned an error; continuing.
tlmgr: package log updated: /home/fes33/.TinyTeX/texmf-var/web2c/tlmgr.log
tlmgr: An error has occurred. See above messages. Exiting.
通过阅读其他一些查询，我发现这是因为镜像 niser.ac.in/ctan/systems/texlive/tlnet 无法正常工作。我尝试了以下解决方案这里但它不起作用：
(running on Debian, switching to user mode!)
(see /usr/share/doc/texlive-base/README.tlmgr-on-Debian.md)
TLPDB: not a directory, not loading: /root/texmf
tlmgr: user mode not initialized, please read the documentation!
我还可以做些什么？