[BeckyEbook]

I really understand this problem and encounter it relatively often, so for me, finding a working solution was crucial.

There was already a discussion on this topic:
https://www.mobileread.com/forums/sh...d.php?t=229308

The problem can be solved in several ways.
a) As suggested by @KevinH – create a validation plugin that will check and report on this issue.

b) Patch for the sanitychecker built into Sigil (\python3lib\sanitycheck.py), which will report the problem when checking (F7).

Spoiler:

Insert before comment "# other special cases"

        # BECKY START
        if tname == "link":
            if "rel=\"stylesheet\"" in s:
                if "type=\"text/css\"" not in s:
                    error_msg = 'Missing type="text/css" in css link tag'
                    self.errors.append((self.tag_start[0], self.tag_start[1], error_msg))
                    self.has_error = True
                    return None, None, None
        # BECKY END

c) Quick-and-dirty patch to clean the code (Mend). Of course, this only applies to those two people who will want to build their own version of Sigil
I know that this is not a perfect solution, but it works fine for my needs.

Spoiler:

File: \src\BookManipulation\CleanSource.cpp
Insert after line 208, before return newsource;

    // Becky START
    QString css_before = " rel=\"stylesheet\"";
    QString css_after  = " type=\"text/css\" rel=\"stylesheet\"";
    newsource.replace(css_before, css_after);
    // Becky END

Personally, I use options b and c.