This issue appears to be standard now.
I'm using TCL 8.6 with Eggdrop 1.8 and have this exact issue.
At a guess, I would say that you started with..
RSS Warning: couldn't open "./scripts/feeds/<name>.db": no such file or directory.
Following that, attempting to make the <name>.db manually, resulting in your error:
RSS Error: Invalid feed database file format (./scripts/<name>.db)!
For me with the first "no such file or directory" also has a second error with it:
RSS Error: Unable to decompress "
http://rss.slashdot.org/Slashdot/slashdot": zlib error (decompressor): invalid stored block lengths
There is a fix for the above zlib decompressor error: (changing the rss-synd.tcl file so use the built-in decompressing which was changed in TCL 8.6) but that appears to be broken too (well for me any way).
This is that fix if anyone is interested:
Changing the rss-synd.tcl by removing the # decompress gzip formatted data lines with the following
# decompress gzip formatted data
proc ::rss-synd::feed_gzip {cdata} {
return $cdata
}
I'd love any help too on getting this working.