Feed throws error (after uninstalling _something_?)

hello,
i installed the grav core (without admin) + blog site (blog skeleton) and started filling it with content.
the site has been working nicely (incl. feeds).
then i decided to try out different themes, and basically installed all themes in the repos (always choosing 'N' when prompted for demo content). i think the last 2 themes in the list (course-companion*) started pulling in what seemed like ALL packages, and i aborted. after that i went over the index and uninstalled a few that seemed safe to remove again.

tried a new theme - feed throws an error ( https://paste.debian.net/409294/ ).
reverted back to antimatter - still the same.

so i'm wondering what could've gone wrong?
my suspicion is that i uninstalled something i shouldn't have.
here's my current gpm index: https://paste.debian.net/?show=409292;lines=0

PS:
thanks for grav, to whomever it may concern! markdown, flat-file, easily editable and comprehensible.

Unfortunately the error says very little. Try first disabling all unused plugins except feed, and remove all unused themes too, see if you can isolate the issue.

@flaviocopes
Unfortunately the error says very little.
yes, i thought the same.
there's another error message on screen, saying:
Server Error
Sorry, something went terribly wrong!
0 - An exception has been thrown during the rendering of a template ("DOMDocumentFragment::appendXML(): Entity: line 1: parser error : error parsing attribute name") in "feed.rss.twig" at line 20.

i will try what you suggest - i suppose "remove" means uninstall via gpm, because that's how i installed the themes.

so, i disabled all plugins except bloginjector + feed, and am getting the same error (afaics - see paste).

then i uninstalled all themes except gateway and antimatter.
still the same error (afaics - see paste).

paste: https://paste.debian.net/409644/

i did, however, notice that 2 themes were noted as "not installed", although they were present in the theme folder. i just deleted the folders.

could it be something went haywire when i interrupted that large install mentioned earlier? is one of the themes supposed to install so much (it was a long flow of wanting to install & reinstall the most basic plugins, i got a little scared and ctrl-c'd).

i found it!
it wasn't related to the install at all, sorry about that.

by elimination i discovered that 2 of my markdown files (blog posts) contained a string like this: <slkdjalksjdasjdlkasjlasj> inside code blocks or inline code - removing the '<>' fixed the feed problem.
strangely, the rest of the site/blog is not affected by this, the strings display as expected in my articles.

Ok glad you found the issue! That is because the feed is built as a XML document and that is interpreted as a tag.

Please report this as an issue on the Feed plugin repository.