I was getting the "mismatched LaTeX support files" error and out of confusion, I ran:

```
sudo fmtutil-user --all
```

Its log said the following:

```
You have run fmtutil-user (as opposed to fmtutil-sys) for the first time;
this has created format files which are local to your personal account.

From now on, any changes in system formats will *not* be automatically
reflected in your files; furthermore, running fmtutil-sys will no longer
have any effect for you.

As a consequence, you yourself have to rerun fmtutil-user after any
change in the system directories. For example, when one of the LaTeX or
other format source files changes, which happens frequently.
See https://tug.org/texlive/scripts-sys-user.html for details.

If you want to undo this, remove the files mentioned above.
```

I don't fully understand the consequences, but I understand that something has gone wrong, because even the linked page advises against using the `user` mode. They have given the instructions to switch back to system mode. I want to do that, but I don't have the directory they have suggested there. The page says:

> For fmtutil, the files in TEXMFVAR/web2c should be backed up and then removed.

My TEXMFVAR contains:

```
~/.texlive2024/texmf-var/fonts
~/.texlive2024/texmf-var/luatex-cache
~/.texlive2024/texmf-var/texdoc
```

Is there anything to worry about? Also, sadly, my original error is still unsolved.